diff --git a/src/compatibility.cpp b/src/compatibility.cpp
index dca0d34851..7339a0f197 100644
--- a/src/compatibility.cpp
+++ b/src/compatibility.cpp
@@ -106,6 +106,7 @@ static FCompatOption Options[] =
 	{ "ignoreteleporttags",		BCOMPATF_BADTELEPORTERS, SLOT_BCOMPAT },
 	{ "rebuildnodes",			BCOMPATF_REBUILDNODES, SLOT_BCOMPAT },
 	{ "linkfrozenprops",		BCOMPATF_LINKFROZENPROPS, SLOT_BCOMPAT },
+	{ "disablepushwindowcheck",	BCOMPATF_NOWINDOWCHECK, SLOT_BCOMPAT },
 
 	// list copied from g_mapinfo.cpp
 	{ "shorttex",				COMPATF_SHORTTEX, SLOT_COMPAT },
diff --git a/src/d_netinfo.cpp b/src/d_netinfo.cpp
index 812f41b037..f3f83e25e5 100644
--- a/src/d_netinfo.cpp
+++ b/src/d_netinfo.cpp
@@ -387,7 +387,7 @@ void D_SetupUserInfo ()
 			{
 			// Some cvars don't copy their original value directly.
 			case NAME_Team:			coninfo->TeamChanged(team); break;
-			case NAME_Skin:			coninfo->SkinChanged(skin); break;
+			case NAME_Skin:			coninfo->SkinChanged(skin, players[consoleplayer].CurrentPlayerClass); break;
 			case NAME_Gender:		coninfo->GenderChanged(gender); break;
 			case NAME_PlayerClass:	coninfo->PlayerClassChanged(playerclass); break;
 			// The rest do.
@@ -447,9 +447,9 @@ int userinfo_t::TeamChanged(int team)
 	return team;
 }
 
-int userinfo_t::SkinChanged(const char *skinname)
+int userinfo_t::SkinChanged(const char *skinname, int playerclass)
 {
-	int skinnum = R_FindSkin(skinname, 0);
+	int skinnum = R_FindSkin(skinname, playerclass);
 	*static_cast<FIntCVar *>((*this)[NAME_Skin]) = skinnum;
 	return skinnum;
 }
@@ -821,7 +821,7 @@ void D_ReadUserInfoStrings (int pnum, BYTE **stream, bool update)
 				break;
 
 			case NAME_Skin:
-				info->SkinChanged(value);
+				info->SkinChanged(value, players[pnum].CurrentPlayerClass);
 				if (players[pnum].mo != NULL)
 				{
 					if (players[pnum].cls != NULL &&
@@ -941,14 +941,21 @@ void WriteUserInfo(FArchive &arc, userinfo_t &info)
 	arc << name;
 }
 
-void ReadUserInfo(FArchive &arc, userinfo_t &info)
+void ReadUserInfo(FArchive &arc, userinfo_t &info, FString &skin)
 {
 	FName name;
 	FBaseCVar **cvar;
 	char *str = NULL;
 	UCVarValue val;
 
+	if (SaveVersion < 4253)
+	{
+		ReadCompatibleUserInfo(arc, info);
+		return;
+	}
+
 	info.Reset();
+	skin = NULL;
 	for (arc << name; name != NAME_None; arc << name)
 	{
 		cvar = info.CheckKey(name);
@@ -958,7 +965,7 @@ void ReadUserInfo(FArchive &arc, userinfo_t &info)
 			switch (name)
 			{
 			case NAME_Team:			info.TeamChanged(atoi(str)); break;
-			case NAME_Skin:			info.SkinChanged(str); break;
+			case NAME_Skin:			skin = str; break;	// Caller must call SkinChanged() once current calss is known
 			case NAME_PlayerClass:	info.PlayerClassChanged(str); break;
 			default:
 				val.String = str;
@@ -973,23 +980,6 @@ void ReadUserInfo(FArchive &arc, userinfo_t &info)
 	}
 }
 
-FArchive &operator<< (FArchive &arc, userinfo_t &info)
-{
-	if (SaveVersion < 4253)
-	{
-		ReadCompatibleUserInfo(arc, info);
-	}
-	else if (arc.IsStoring())
-	{
-		WriteUserInfo(arc, info);
-	}
-	else
-	{
-		ReadUserInfo(arc, info);
-	}
-	return arc;
-}
-
 CCMD (playerinfo)
 {
 	if (argv.argc() < 2)
diff --git a/src/d_player.h b/src/d_player.h
index 22f01f4907..4da0e9d10b 100644
--- a/src/d_player.h
+++ b/src/d_player.h
@@ -333,7 +333,7 @@ struct userinfo_t : TMap<FName,FBaseCVar *>
 
 	void Reset();
 	int TeamChanged(int team);
-	int SkinChanged(const char *skinname);
+	int SkinChanged(const char *skinname, int playerclass);
 	int SkinNumChanged(int skinnum);
 	int GenderChanged(const char *gendername);
 	int PlayerClassChanged(const char *classname);
@@ -343,8 +343,8 @@ struct userinfo_t : TMap<FName,FBaseCVar *>
 	int ColorSetChanged(int setnum);
 };
 
-FArchive &operator<< (FArchive &arc, userinfo_t &info);
-
+void ReadUserInfo(FArchive &arc, userinfo_t &info, FString &skin);
+void WriteUserInfo(FArchive &arc, userinfo_t &info);
 
 //
 // Extended player object info: player_t
diff --git a/src/doomdef.h b/src/doomdef.h
index e08c3044d6..6ef9fcd041 100644
--- a/src/doomdef.h
+++ b/src/doomdef.h
@@ -351,6 +351,7 @@ enum
 	BCOMPATF_BADPORTALS			= 1 << 4,	// Restores the old unstable portal behavior
 	BCOMPATF_REBUILDNODES		= 1 << 5,	// Force node rebuild
 	BCOMPATF_LINKFROZENPROPS	= 1 << 6,	// Clearing PROP_TOTALLYFROZEN or PROP_FROZEN also clears the other
+	BCOMPATF_NOWINDOWCHECK		= 1 << 7,	// Disable the window check in CheckForPushSpecial()
 };
 
 // phares 3/20/98:
diff --git a/src/oplsynth/opl_mus_player.cpp b/src/oplsynth/opl_mus_player.cpp
index 335e6d66e1..a528c10e2b 100644
--- a/src/oplsynth/opl_mus_player.cpp
+++ b/src/oplsynth/opl_mus_player.cpp
@@ -96,7 +96,7 @@ fail:		delete[] scoredata;
 	else if (((DWORD *)scoredata)[0] == MAKE_ID('D','B','R','A') &&
 		((DWORD *)scoredata)[1] == MAKE_ID('W','O','P','L'))
 	{
-		if (((DWORD *)scoredata)[2] == MAKE_ID(0,0,1,0))
+		if (LittleShort(((WORD *)scoredata)[5]) == 1)
 		{
 			RawPlayer = DosBox1;
 			SamplesPerTick = OPL_SAMPLE_RATE / 1000;
@@ -104,16 +104,19 @@ fail:		delete[] scoredata;
 		}
 		else if (((DWORD *)scoredata)[2] == MAKE_ID(2,0,0,0))
 		{
-			if (scoredata[20] != 0)
-			{
-				Printf("Unsupported DOSBox Raw OPL format %d\n", scoredata[20]);
-				goto fail;
-			}
+			bool okay = true;
 			if (scoredata[21] != 0)
 			{
-				Printf("Unsupported DOSBox Raw OPL compression %d\n", scoredata[21]);
-				goto fail;
+				Printf("Unsupported DOSBox Raw OPL format %d\n", scoredata[20]);
+				okay = false;
 			}
+			if (scoredata[22] != 0)
+			{
+				Printf("Unsupported DOSBox Raw OPL compression %d\n", scoredata[21]);
+				okay = false;
+			}
+			if (!okay)
+				goto fail;
 			RawPlayer = DosBox2;
 			SamplesPerTick = OPL_SAMPLE_RATE / 1000;
 			int headersize = 0x1A + scoredata[0x19];
@@ -264,7 +267,7 @@ bool OPLmusicBlock::ServiceStream (void *buff, int numbytes)
 					{
 						for (i = 0; i < io->NumChips; ++i)
 						{
-							io->chips[i]->Update(samples1, samplesleft);
+							io->chips[i]->Update(samples1, numsamples);
 						}
 						OffsetSamples(samples1, numsamples << stereoshift);
 					}
diff --git a/src/p_map.cpp b/src/p_map.cpp
index 0e66ee58d9..d900c2a46c 100644
--- a/src/p_map.cpp
+++ b/src/p_map.cpp
@@ -1640,7 +1640,7 @@ static void CheckForPushSpecial (line_t *line, int side, AActor *mobj, bool wind
 {
 	if (line->special && !(mobj->flags6 & MF6_NOTRIGGER))
 	{
-		if (windowcheck && line->backsector != NULL)
+		if (windowcheck && !(ib_compatflags & BCOMPATF_NOWINDOWCHECK) && line->backsector != NULL)
 		{ // Make sure this line actually blocks us and is not a window
 		  // or similar construct we are standing inside of.
 			fixed_t fzt = line->frontsector->ceilingplane.ZatPoint(mobj->x, mobj->y);
diff --git a/src/p_slopes.cpp b/src/p_slopes.cpp
index 07ddf2e0d7..af0ad7a205 100644
--- a/src/p_slopes.cpp
+++ b/src/p_slopes.cpp
@@ -178,6 +178,12 @@ void P_SetSlope (secplane_t *plane, bool setCeil, int xyangi, int zangi,
 	}
 	zang >>= ANGLETOFINESHIFT;
 
+	// Sanitize xyangi to [0,360) range
+	xyangi = xyangi % 360;
+	if (xyangi < 0)
+	{
+		xyangi = 360 + xyangi;
+	}
 	xyang = (angle_t)Scale (xyangi, ANGLE_90, 90 << ANGLETOFINESHIFT);
 
 	FVector3 norm;
@@ -446,11 +452,11 @@ void P_SpawnSlopeMakers (FMapThing *firstmt, FMapThing *lastmt, const int *oldve
 				P_VavoomSlope(sec, mt->thingid, x, y, mt->z, mt->type & 1); 
 			}
 			else if (mt->type <= THING_SlopeCeilingPointLine)
-			{
+			{ // THING_SlopeFloorPointLine and THING_SlopCeilingPointLine
 				P_SlopeLineToPoint (mt->args[0], x, y, z, mt->type & 1);
 			}
 			else
-			{
+			{ // THING_SetFloorSlope and THING_SetCeilingSlope
 				P_SetSlope (refplane, mt->type & 1, mt->angle, mt->args[0], x, y, z);
 			}
 			mt->type = 0;
diff --git a/src/p_user.cpp b/src/p_user.cpp
index 14fa9c12c5..e1b0210efa 100644
--- a/src/p_user.cpp
+++ b/src/p_user.cpp
@@ -2746,14 +2746,22 @@ void P_UnPredictPlayer ()
 void player_t::Serialize (FArchive &arc)
 {
 	int i;
+	FString skinname;
 
 	arc << cls
 		<< mo
 		<< camera
 		<< playerstate
-		<< cmd
-		<< userinfo
-		<< DesiredFOV << FOV
+		<< cmd;
+	if (arc.IsLoading())
+	{
+		ReadUserInfo(arc, userinfo, skinname);
+	}
+	else
+	{
+		WriteUserInfo(arc, userinfo);
+	}
+	arc << DesiredFOV << FOV
 		<< viewz
 		<< viewheight
 		<< deltaviewheight
@@ -2904,6 +2912,10 @@ void player_t::Serialize (FArchive &arc)
 		oldbuttons = ~0;
 		original_oldbuttons = ~0;
 	}
+	if (skinname.IsNotEmpty())
+	{
+		userinfo.SkinChanged(skinname, CurrentPlayerClass);
+	}
 }
 
 
diff --git a/src/textures/multipatchtexture.cpp b/src/textures/multipatchtexture.cpp
index fd2b59fb16..4f327309dd 100644
--- a/src/textures/multipatchtexture.cpp
+++ b/src/textures/multipatchtexture.cpp
@@ -244,7 +244,6 @@ FMultiPatchTexture::FMultiPatchTexture (const void *texdef, FPatchLookup *patchl
 	Height = SAFESHORT(mtexture.d->height);
 	strncpy (Name, (const char *)mtexture.d->name, 8);
 	Name[8] = 0;
-
 	CalcBitSize ();
 
 	xScale = mtexture.d->ScaleX ? mtexture.d->ScaleX*(FRACUNIT/8) : FRACUNIT;
@@ -280,6 +279,10 @@ FMultiPatchTexture::FMultiPatchTexture (const void *texdef, FPatchLookup *patchl
 			NumParts--;
 			i--;
 		}
+		else
+		{
+			Parts[i].Texture->bKeepAround = true;
+		}
 		if (strife)
 			mpatch.s++;
 		else
@@ -859,7 +862,6 @@ void FTextureManager::AddTexturesLump (const void *lumpdata, int lumpsize, int d
 		{
 			pnames.Read (patchlookup[i].Name, 8);
 			patchlookup[i].Name[8] = 0;
-
 			FTextureID j = CheckForTexture (patchlookup[i].Name, FTexture::TEX_WallPatch);
 			if (j.isValid())
 			{
diff --git a/src/textures/texture.cpp b/src/textures/texture.cpp
index 093bf303b5..0434aaaa4e 100644
--- a/src/textures/texture.cpp
+++ b/src/textures/texture.cpp
@@ -146,7 +146,7 @@ FTexture::FTexture (const char *name, int lumpnum)
 : LeftOffset(0), TopOffset(0),
   WidthBits(0), HeightBits(0), xScale(FRACUNIT), yScale(FRACUNIT), SourceLump(lumpnum),
   UseType(TEX_Any), bNoDecals(false), bNoRemap0(false), bWorldPanning(false),
-  bMasked(true), bAlphaTexture(false), bHasCanvas(false), bWarped(0), bComplex(false), bMultiPatch(false),
+  bMasked(true), bAlphaTexture(false), bHasCanvas(false), bWarped(0), bComplex(false), bMultiPatch(false), bKeepAround(false),
   Rotations(0xFFFF), SkyOffset(0), Width(0), Height(0), WidthMask(0), Native(NULL)
 {
 	id.SetInvalid();
diff --git a/src/textures/texturemanager.cpp b/src/textures/texturemanager.cpp
index f28026f193..48f3ff9e02 100644
--- a/src/textures/texturemanager.cpp
+++ b/src/textures/texturemanager.cpp
@@ -428,7 +428,7 @@ void FTextureManager::ReplaceTexture (FTextureID picnum, FTexture *newtexture, b
 	Textures[index].Texture = newtexture;
 
 	newtexture->id = oldtexture->id;
-	if (free)
+	if (free && !oldtexture->bKeepAround)
 	{
 		delete oldtexture;
 	}
diff --git a/src/textures/textures.h b/src/textures/textures.h
index 100ba31e9e..837c62689c 100644
--- a/src/textures/textures.h
+++ b/src/textures/textures.h
@@ -177,6 +177,7 @@ public:
 							// fully composited before subjected to any kind of postprocessing instead of
 							// doing it per patch.
 	BYTE bMultiPatch:1;		// This is a multipatch texture (we really could use real type info for textures...)
+	BYTE bKeepAround:1;		// This texture was used as part of a multi-patch texture. Do not free it.
 
 	WORD Rotations;
 	SWORD SkyOffset;
diff --git a/wadsrc/static/compatibility.txt b/wadsrc/static/compatibility.txt
index 4b75dfaba3..e2516a30d6 100644
--- a/wadsrc/static/compatibility.txt
+++ b/wadsrc/static/compatibility.txt
@@ -375,4 +375,9 @@ D62DCA9EC226DE49108D5DD9271F7631 // Cheogsh 2 map04
 	setthingz 1647 528
 	setthingz 1648 528
 	setthingz 1649 528
-}
\ No newline at end of file
+}
+
+B9DFF13207EACAC675C71D82624D0007 // XtheaterIII map01
+{
+	DisablePushWindowCheck
+}