diff --git a/src/gl/data/gl_data.cpp b/src/gl/data/gl_data.cpp
index e0bb5ee6b..385b7409b 100644
--- a/src/gl/data/gl_data.cpp
+++ b/src/gl/data/gl_data.cpp
@@ -438,7 +438,6 @@ void gl_RecalcVertexHeights(vertex_t * v)
 	int i,j,k;
 	float height;
 
-	//@sync-vertexheights
 	v->numheights=0;
 	for(i=0;i<v->numsectors;i++)
 	{
diff --git a/src/gl/scene/gl_drawinfo.cpp b/src/gl/scene/gl_drawinfo.cpp
index 62e604aca..f078c52c9 100644
--- a/src/gl/scene/gl_drawinfo.cpp
+++ b/src/gl/scene/gl_drawinfo.cpp
@@ -855,7 +855,6 @@ void GLDrawList::Sort()
 //==========================================================================
 void GLDrawList::AddWall(GLWall * wall)
 {
-	//@sync-drawinfo
 	drawitems.Push(GLDrawItem(GLDIT_WALL,walls.Push(*wall)));
 }
 
@@ -866,7 +865,6 @@ void GLDrawList::AddWall(GLWall * wall)
 //==========================================================================
 void GLDrawList::AddFlat(GLFlat * flat)
 {
-	//@sync-drawinfo
 	drawitems.Push(GLDrawItem(GLDIT_FLAT,flats.Push(*flat)));
 }
 
@@ -877,7 +875,6 @@ void GLDrawList::AddFlat(GLFlat * flat)
 //==========================================================================
 void GLDrawList::AddSprite(GLSprite * sprite)
 {	
-	//@sync-drawinfo
 	drawitems.Push(GLDrawItem(GLDIT_SPRITE,sprites.Push(*sprite)));
 }
 
diff --git a/src/gl/scene/gl_renderhacks.cpp b/src/gl/scene/gl_renderhacks.cpp
index a6452a01f..7aba676f5 100644
--- a/src/gl/scene/gl_renderhacks.cpp
+++ b/src/gl/scene/gl_renderhacks.cpp
@@ -163,7 +163,6 @@ void FDrawInfo::AddUpperMissingTexture(side_t * side, subsector_t *sub, fixed_t
 				return;
 			}
 
-			//@sync-hack
 			for(unsigned int i=0;i<MissingUpperTextures.Size();i++)
 			{
 				if (MissingUpperTextures[i].sub == sub)
@@ -230,13 +229,12 @@ void FDrawInfo::AddLowerMissingTexture(side_t * side, subsector_t *sub, fixed_t
 			}
 
 			// Ignore FF_FIX's because they are designed to abuse missing textures
-			if (seg->backsector->e->XFloor.ffloors.Size() && seg->backsector->e->XFloor.ffloors[0]->flags&FF_FIX)
+			if (seg->backsector->e->XFloor.ffloors.Size() && (seg->backsector->e->XFloor.ffloors[0]->flags&(FF_FIX|FF_SEETHROUGH)) == FF_FIX)
 			{
 				totalms.Unclock();
 				return;
 			}
 
-			//@sync-hack
 			for(unsigned int i=0;i<MissingLowerTextures.Size();i++)
 			{
 				if (MissingLowerTextures[i].sub == sub)
@@ -733,7 +731,6 @@ void FDrawInfo::AddHackedSubsector(subsector_t * sub)
 {
 	if (!(level.maptype == MAPTYPE_HEXEN))
 	{
-		//@sync-hack (probably not, this is only called from the main thread)
 		SubsectorHackInfo sh={sub, 0};
 		SubsectorHacks.Push (sh);
 	}
@@ -1033,13 +1030,11 @@ ADD_STAT(sectorhacks)
 
 void FDrawInfo::AddFloorStack(sector_t * sec)
 {
-	//@sync-hack
 	FloorStacks.Push(sec);
 }
 
 void FDrawInfo::AddCeilingStack(sector_t * sec)
 {
-	//@sync-hack
 	CeilingStacks.Push(sec);
 }
 
diff --git a/src/gl/scene/gl_walls.cpp b/src/gl/scene/gl_walls.cpp
index 2d14e0949..84e7e5636 100644
--- a/src/gl/scene/gl_walls.cpp
+++ b/src/gl/scene/gl_walls.cpp
@@ -199,7 +199,6 @@ void GLWall::PutWall(bool translucent)
 	// portals don't go into the draw list.
 	// Instead they are added to the portal manager
 	case RENDERWALL_HORIZON:
-		//@sync-portal
 		horizon=UniqueHorizons.Get(horizon);
 		portal=GLPortal::FindPortal(horizon);
 		if (!portal) portal=new GLHorizonPortal(horizon);
@@ -207,14 +206,12 @@ void GLWall::PutWall(bool translucent)
 		break;
 
 	case RENDERWALL_SKYBOX:
-		//@sync-portal
 		portal=GLPortal::FindPortal(skybox);
 		if (!portal) portal=new GLSkyboxPortal(skybox);
 		portal->AddLine(this);
 		break;
 
 	case RENDERWALL_SECTORSTACK:
-		//@sync-portal
 		portal = this->portal->GetGLPortal();
 		portal->AddLine(this);
 		break;
@@ -231,7 +228,6 @@ void GLWall::PutWall(bool translucent)
 		break;
 
 	case RENDERWALL_MIRROR:
-		//@sync-portal
 		portal=GLPortal::FindPortal(seg->linedef);
 		if (!portal) portal=new GLMirrorPortal(seg->linedef);
 		portal->AddLine(this);
@@ -244,7 +240,6 @@ void GLWall::PutWall(bool translucent)
 		break;
 
 	case RENDERWALL_SKY:
-		//@sync-portal
 		portal=GLPortal::FindPortal(sky);
 		if (!portal) portal=new GLSkyPortal(sky);
 		portal->AddLine(this);
diff --git a/src/gl/textures/gl_material.cpp b/src/gl/textures/gl_material.cpp
index 5e9a9be1a..500a0afab 100644
--- a/src/gl/textures/gl_material.cpp
+++ b/src/gl/textures/gl_material.cpp
@@ -1047,7 +1047,6 @@ FMaterial * FMaterial::ValidateTexture(FTexture * tex)
 		FMaterial *gltex = tex->gl_info.Material;
 		if (gltex == NULL) 
 		{
-			//@sync-tex
 			gltex = new FMaterial(tex, false);
 		}
 		return gltex;
diff --git a/src/p_3dfloors.cpp b/src/p_3dfloors.cpp
index ce6224b53..67933a75a 100644
--- a/src/p_3dfloors.cpp
+++ b/src/p_3dfloors.cpp
@@ -264,6 +264,7 @@ static int P_Set3DFloor(line_t * line, int param, int param2, int alpha)
 		else if (param==4)
 		{
 			flags=FF_EXISTS|FF_RENDERPLANES|FF_INVERTPLANES|FF_NOSHADE|FF_FIX;
+			if (param2 & 1) flags |= FF_SEETHROUGH;	// marker for allowing missing texture checks
 			alpha=255;
 		}
 		else 
diff --git a/wadsrc/static/compatibility.txt b/wadsrc/static/compatibility.txt
index 1c2307ec0..bf5f3cc3b 100644
--- a/wadsrc/static/compatibility.txt
+++ b/wadsrc/static/compatibility.txt
@@ -381,3 +381,17 @@ B9DFF13207EACAC675C71D82624D0007 // XtheaterIII map01
 {
 	DisablePushWindowCheck
 }
+
+712BB4CFBD0753178CA0C6814BE4C288 // map12 BTSX_E1 - patch some rendering glitches that are problematic to detect
+{
+	setsectortag 545 32000
+	setsectortag 1618 32000
+	setlinespecial 2853 Sector_Set3DFloor 32000 4 0 0 0
+	setsectortag 439 32001
+	setsectortag 458 32001
+	setlinespecial 2182 Sector_Set3DFloor 32001 4 0 0 0
+	setsectortag 454 32002
+	setsectortag 910 32002
+	setlinespecial 2410 Sector_Set3DFloor 32002 4 1 0 0
+}
+