diff --git a/.gitignore b/.gitignore
index c72578915..fb6bc8530 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,59 +1,26 @@
-/Debug
 *.ncb
 *.suo
 *.pdb
 *.ilk
 *.aps
-/fmodapi*/
-/Release
 /wadsrc_wad
 *.user
 /build
-/debug
-/release
-*/debug
-*/release
 /release_gcc
-/dumb/vc6/dumb_static/release
-/dumb/vc6/dumb_static/debug
-/dumb/vc6/dumb_static/x64
 /DOOMSTATS.TXT
 /src/gitinfo.h
-/src/sc_man_scanner.h
-/src/xlat/xlat_parser.c
-/src/xlat/xlat_parser.h
-/src/xlat/xlat_parser.out
-/src/zscript/zcc-parse.c
-/src/zscript/zcc-parse.h
-/src/zscript/zcc-parse.out
-/tools/*/debug
-/tools/*/release
-/tools/*/*.exe
-/tools/lemon/build
-/tools/re2c/build
-/tools/updaterevision/x64/
-/tools/zipdir/x64
 /wadsrc/*.pk3
-/build_vc2013
-/bzip2/x64/
 /disasm.txt
-/game-music-emu/x64/
-/gdtoa/x64/
-/jpeg-6b/x64/
-/lzma/x64/
-/zlib/x64/
-/build_vc2013_64bit
 /build_vc2015
 /build_vc2015-32
 /build_vc2015-64
 /build_vc2017-64
 /build
 /llvm
-/src/r_drawersasm.obj
-/src/r_drawersasm.o
 .vs
 /src/gl/unused
 /mapfiles_release/*.map
 .DS_Store
 /build_vc2017-32
 /build2
+/build_vc2019-64
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 8e6d07fb4..1184dd150 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1456,12 +1456,12 @@ source_group("External\\SFMT" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/s
 source_group("FraggleScript" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/fragglescript/.+")
 source_group("Game Data" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/gamedata/.+")
 source_group("Game Data\\Resource Files" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/gamedata/resourcefiles/.+")
-source_group("Game Data\\Textures" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/textures/.+")
-source_group("Game Data\\Textures\\Hires" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/textures/hires/.+")
-source_group("Game Data\\Textures\\Hires\\HQ Resize" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/textures/hires/hqnx/.+")
-source_group("Game Data\\Textures\\Hires\\HQ Resize MMX version" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/textures/hires/hqnx_asm/.+")
-source_group("Game Data\\Textures\\Hires\\XBRZ" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/textures/hires/xbr/.+")
-source_group("Game Data\\Textures\\Formats" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/textures/formats/.+")
+source_group("Game Data\\Textures" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/gamedata/textures/.+")
+source_group("Game Data\\Textures\\Hires" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/gamedata/textures/hires/.+")
+source_group("Game Data\\Textures\\Hires\\HQ Resize" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/gamedata/textures/hires/hqnx/.+")
+source_group("Game Data\\Textures\\Hires\\HQ Resize MMX version" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/gamedata/textures/hires/hqnx_asm/.+")
+source_group("Game Data\\Textures\\Hires\\XBRZ" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/gamedata/textures/hires/xbr/.+")
+source_group("Game Data\\Textures\\Formats" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/gamedata/textures/formats/.+")
 source_group("Intermission" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/intermission/.+")
 source_group("Map Loader" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/maploader/.+")
 source_group("Menu" REGULAR_EXPRESSION "^${CMAKE_CURRENT_SOURCE_DIR}/menu/.+")
diff --git a/src/d_main.cpp b/src/d_main.cpp
index b6c723704..cc684976d 100644
--- a/src/d_main.cpp
+++ b/src/d_main.cpp
@@ -600,7 +600,7 @@ CUSTOM_CVAR(Int, compatmode, 0, CVAR_ARCHIVE|CVAR_NOINITCALL)
 
 	case 4: // Old ZDoom compat mode
 		v = COMPATF_SOUNDTARGET | COMPATF_LIGHT;
-		w = COMPATF2_MULTIEXIT | COMPATF2_TELEPORT | COMPATF2_PUSHWINDOW;
+		w = COMPATF2_MULTIEXIT | COMPATF2_TELEPORT | COMPATF2_PUSHWINDOW | COMPATF2_CHECKSWITCHRANGE;
 		break;
 
 	case 5: // MBF compat mode
@@ -658,6 +658,7 @@ CVAR (Flag, compat_pointonline,			compatflags2, COMPATF2_POINTONLINE);
 CVAR (Flag, compat_multiexit,			compatflags2, COMPATF2_MULTIEXIT);
 CVAR (Flag, compat_teleport,			compatflags2, COMPATF2_TELEPORT);
 CVAR (Flag, compat_pushwindow,			compatflags2, COMPATF2_PUSHWINDOW);
+CVAR (Flag, compat_checkswitchrange,	compatflags2, COMPATF2_CHECKSWITCHRANGE);
 
 CVAR(Bool, vid_activeinbackground, false, CVAR_ARCHIVE | CVAR_GLOBALCONFIG)
 
diff --git a/src/doomdef.h b/src/doomdef.h
index a8f0250d5..14d029f8b 100644
--- a/src/doomdef.h
+++ b/src/doomdef.h
@@ -328,6 +328,7 @@ enum : unsigned int
 	COMPATF2_MULTIEXIT		= 1 << 4,	// Level exit can be triggered multiple times (required by Daedalus's travel tubes, thanks to a faulty script)
 	COMPATF2_TELEPORT		= 1 << 5,	// Don't let indirect teleports trigger sector actions
 	COMPATF2_PUSHWINDOW		= 1 << 6,	// Disable the window check in CheckForPushSpecial()
+	COMPATF2_CHECKSWITCHRANGE = 1 << 7,	// Enable buggy CheckSwitchRange behavior
 };
 
 // Emulate old bugs for select maps. These are not exposed by a cvar
diff --git a/src/g_levellocals.h b/src/g_levellocals.h
index 57fa440b9..afa6dd454 100644
--- a/src/g_levellocals.h
+++ b/src/g_levellocals.h
@@ -600,7 +600,6 @@ public:
 	int			airsupply;
 	int			DefaultEnvironment;		// Default sound environment.
 
-	int ActiveSequences;
 	DSeqNode *SequenceListHead;
 
 	// [RH] particle globals
diff --git a/src/g_shared/p_switch.cpp b/src/g_shared/p_switch.cpp
index 2e092b5c3..81ce5b58b 100644
--- a/src/g_shared/p_switch.cpp
+++ b/src/g_shared/p_switch.cpp
@@ -194,7 +194,9 @@ bool P_CheckSwitchRange(AActor *user, line_t *line, int sideno, const DVector3 *
 			}
 		}
 
-		return (user->Top() > open.top);
+		return (user->Level->i_compatflags2 & COMPATF2_CHECKSWITCHRANGE)
+			? (user->Top() >= open.top)
+			: (user->Top() > open.top);
 	}
 	else if ((TexMan.FindSwitch(side->GetTexture(side_t::bottom))) != NULL)
 	{
@@ -216,7 +218,9 @@ bool P_CheckSwitchRange(AActor *user, line_t *line, int sideno, const DVector3 *
 			}
 		}
 
-		return (user->Z() < open.bottom);
+		return (user->Level->i_compatflags2 & COMPATF2_CHECKSWITCHRANGE)
+			? (user->Z() <= open.bottom)
+			: (user->Z() < open.bottom);
 	}
 	else if ((flags & ML_3DMIDTEX) || (TexMan.FindSwitch(side->GetTexture(side_t::mid))) != NULL)
 	{
@@ -229,7 +233,9 @@ bool P_CheckSwitchRange(AActor *user, line_t *line, int sideno, const DVector3 *
 	else
 	{
 		// no switch found. Check whether the player can touch either top or bottom texture
-		return (user->Top() > open.top) || (user->isBelow(open.bottom));
+		return (user->Level->i_compatflags2 & COMPATF2_CHECKSWITCHRANGE)
+			? ( (user->Top() >= open.top) || (user->Z() <= open.bottom) )
+			: ( (user->Top() > open.top)  || user->isBelow(open.bottom) );
 	}
 }
 
diff --git a/src/gamedata/g_mapinfo.cpp b/src/gamedata/g_mapinfo.cpp
index c7e20de09..73c7aaf42 100644
--- a/src/gamedata/g_mapinfo.cpp
+++ b/src/gamedata/g_mapinfo.cpp
@@ -1641,6 +1641,7 @@ MapFlagHandlers[] =
 	{ "compat_multiexit",				MITYPE_COMPATFLAG, 0, COMPATF2_MULTIEXIT },
 	{ "compat_teleport",				MITYPE_COMPATFLAG, 0, COMPATF2_TELEPORT },
 	{ "compat_pushwindow",				MITYPE_COMPATFLAG, 0, COMPATF2_PUSHWINDOW },
+	{ "compat_checkswitchrange",		MITYPE_COMPATFLAG, 0, COMPATF2_CHECKSWITCHRANGE },
 	{ "cd_start_track",					MITYPE_EATNEXT,	0, 0 },
 	{ "cd_end1_track",					MITYPE_EATNEXT,	0, 0 },
 	{ "cd_end2_track",					MITYPE_EATNEXT,	0, 0 },
diff --git a/src/maploader/compatibility.cpp b/src/maploader/compatibility.cpp
index ad792dc5a..61c3106c4 100644
--- a/src/maploader/compatibility.cpp
+++ b/src/maploader/compatibility.cpp
@@ -164,6 +164,7 @@ static FCompatOption Options[] =
 	{ "multiexit",				COMPATF2_MULTIEXIT, SLOT_COMPAT2 },
 	{ "teleport",				COMPATF2_TELEPORT, SLOT_COMPAT2 },
 	{ "disablepushwindowcheck",	COMPATF2_PUSHWINDOW, SLOT_COMPAT2 },
+	{ "checkswitchrange",		COMPATF2_CHECKSWITCHRANGE, SLOT_COMPAT2 },
 	{ NULL, 0, 0 }
 };
 
diff --git a/src/p_saveg.cpp b/src/p_saveg.cpp
index 63b3fe9a6..55c04c944 100644
--- a/src/p_saveg.cpp
+++ b/src/p_saveg.cpp
@@ -932,7 +932,6 @@ void FLevelLocals::Serialize(FSerializer &arc, bool hubload)
 		Thinkers.DestroyAllThinkers();
 		interpolator.ClearInterpolations();
 		arc.ReadObjects(hubload);
-		ActiveSequences = 0;
 	}
 
 	arc("multiplayer", multiplayer);
diff --git a/src/s_sndseq.cpp b/src/s_sndseq.cpp
index 3d5b347e1..a9bfda24e 100644
--- a/src/s_sndseq.cpp
+++ b/src/s_sndseq.cpp
@@ -406,7 +406,6 @@ void DSeqNode::OnDestroy()
 		m_Next->m_Prev = m_Prev;
 		GC::WriteBarrier(m_Next, m_Prev);
 	}
-	Level->ActiveSequences--;
 	Super::OnDestroy();
 }
 
@@ -827,7 +826,6 @@ void DSeqNode::ActivateSequence (int sequence)
 	m_CurrentSoundID = 0;
 	m_Volume = 1;			// Start at max volume...
 	m_Atten = ATTN_IDLE;	// ...and idle attenuation
-	Level->ActiveSequences++;
 }
 
 DSeqActorNode::DSeqActorNode (AActor *actor, int sequence, int modenum)
@@ -1323,7 +1321,6 @@ void DSeqNode::Tick ()
 						int seqnum = FindSequence (ENamedName(m_SequencePtr[i*2+1]));
 						if (seqnum >= 0)
 						{ // Found a match, and it's a good one too.
-							Level->ActiveSequences--;
 							ActivateSequence (seqnum);
 							break;
 						}
@@ -1358,7 +1355,7 @@ void SN_UpdateActiveSequences (FLevelLocals *Level)
 {
 	DSeqNode *node;
 
-	if (!Level->ActiveSequences || paused)
+	if (paused)
 	{ // No sequences currently playing/game is paused
 		return;
 	}
diff --git a/wadsrc/static/compatibility.txt b/wadsrc/static/compatibility.txt
index 2ab378ba3..a5fbe691a 100644
--- a/wadsrc/static/compatibility.txt
+++ b/wadsrc/static/compatibility.txt
@@ -261,8 +261,6 @@ FA23E72FA955E66EC68609F72C0BA71E // unloved.pk3:unlovedmaps.wad map02
 41BEC1F643CFEEC997AF98276A05EC88 // unloved.pk3:unlovedmaps.wad map03
 AF9A6370BE562584BC11165ECF364713 // unloved.pk3:unlovedmaps.wad map04
 DC96228097DD004C40CCB1DB14A91EAA // unloved.pk3:unlovedmaps.wad map05
-261E64897A572C8DB8DC041E64BE27AD // unloved2beta1.pk3:u2_new2maps2.wad map06
-04800B1F35E8C036EBABC8C616402927 // unloved2beta1.pk3:u2_new2maps2.wad map07
 9E54F70648A77BBD090FF78A3AA05367 // unloved2beta1.pk3:u2_new2maps2.wad map08
 72E9E0F41F691B7F956E62F35B4A617F // unloved2beta1.pk3:u2_new2maps2.wad map09
 3D3FE412E87AD8B2316DAEC9E25F2E5D // unloved2beta1.pk3:u2_new2maps2.wad map10
@@ -275,3 +273,15 @@ DC96228097DD004C40CCB1DB14A91EAA // unloved.pk3:unlovedmaps.wad map05
 	setslopeoverflow
 	polyobj
 }
+
+1624AD80349566AA7F29D2CA0D51754B // The Gateway Experiments Episode 5: Prime Directive, ge5map02
+{
+	checkswitchrange
+}
+
+261E64897A572C8DB8DC041E64BE27AD // unloved2beta1.pk3:u2_new2maps2.wad map06
+04800B1F35E8C036EBABC8C616402927 // unloved2beta1.pk3:u2_new2maps2.wad map07
+{
+	clipmidtex
+	checkswitchrange
+}
diff --git a/wadsrc/static/language.enu b/wadsrc/static/language.enu
index 736c578e0..6e8635a15 100644
--- a/wadsrc/static/language.enu
+++ b/wadsrc/static/language.enu
@@ -2184,6 +2184,7 @@ CMPTMNU_SOUNDCUTOFF			= "Sounds stop when actor vanishes";
 CMPTMNU_SOUNDTARGET			= "Use original sound target handling";
 CMPTMNU_TELEPORT			= "Scripted teleports don't trigger sector actions";
 CMPTMNU_PUSHWINDOW			= "Non-blocking lines can be pushed";
+CMPTMNU_CHECKSWITCHRANGE	= "Enable buggy CheckSwitchRange behavior";
 
 // Sound Options
 SNDMNU_TITLE			= "SOUND OPTIONS";
diff --git a/wadsrc/static/menudef.txt b/wadsrc/static/menudef.txt
index 6633265f2..2a6fe6a65 100644
--- a/wadsrc/static/menudef.txt
+++ b/wadsrc/static/menudef.txt
@@ -1434,6 +1434,7 @@ OptionMenu "CompatibilityOptions" protected
 	Option "$CMPTMNU_MULTIEXIT",					"compat_multiexit", "YesNo"
 	Option "$CMPTMNU_TELEPORT",						"compat_teleport", "YesNo"
 	Option "$CMPTMNU_PUSHWINDOW",					"compat_pushwindow", "YesNo"
+	Option "$CMPTMNU_CHECKSWITCHRANGE",				"compat_checkswitchrange", "YesNo"
 
 	StaticText " "
 	StaticText "$CMPTMNU_PHYSICSBEHAVIOR",1
diff --git a/wadsrc/static/zscript/constants.txt b/wadsrc/static/zscript/constants.txt
index 0de7ec391..0df017485 100644
--- a/wadsrc/static/zscript/constants.txt
+++ b/wadsrc/static/zscript/constants.txt
@@ -1338,4 +1338,5 @@ enum ECompatFlags
 	COMPATF2_MULTIEXIT		= 1 << 4,	// Level exit can be triggered multiple times (required by Daedalus's travel tubes, thanks to a faulty script)
 	COMPATF2_TELEPORT		= 1 << 5,	// Don't let indirect teleports trigger sector actions
 	COMPATF2_PUSHWINDOW		= 1 << 6,	// Disable the window check in CheckForPushSpecial()
+	COMPATF2_CHECKSWITCHRANGE = 1 << 7,	// Enable buggy CheckSwitchRange behavior
 };