diff --git a/src/p_mobj.c b/src/p_mobj.c
index 2cf94e835..a5ed98846 100644
--- a/src/p_mobj.c
+++ b/src/p_mobj.c
@@ -2028,12 +2028,14 @@ static void P_AdjustMobjFloorZ_FFloors(mobj_t *mo, sector_t *sector, UINT8 motyp
 		delta1 = mo->z - (bottomheight + ((topheight - bottomheight)/2));
 		delta2 = thingtop - (bottomheight + ((topheight - bottomheight)/2));
 		if (topheight > mo->floorz && abs(delta1) < abs(delta2)
-			&& !(rover->flags & FF_REVERSEPLATFORM))
+			&& !(rover->flags & FF_REVERSEPLATFORM)
+			&& ((P_MobjFlip(mo)*mo->momz > 0) || (!(rover->flags & FF_PLATFORM)))) // In reverse gravity, only clip for FOFs that are intangible from their bottom (the "top" you're falling through) if you're coming from above ("below" in your frame of reference)
 		{
 			mo->floorz = topheight;
 		}
 		if (bottomheight < mo->ceilingz && abs(delta1) >= abs(delta2)
-			&& !(rover->flags & FF_PLATFORM))
+			&& !(rover->flags & FF_PLATFORM)
+			&& ((P_MobjFlip(mo)*mo->momz > 0) || (!(rover->flags & FF_REVERSEPLATFORM)))) // In normal gravity, only clip for FOFs that are intangible from the top if you're coming from below
 		{
 			mo->ceilingz = bottomheight;
 		}
diff --git a/src/p_setup.c b/src/p_setup.c
index b36bf0b80..6c14e3614 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -1931,10 +1931,18 @@ static void P_GroupLines(void)
 	// allocate linebuffers for each sector
 	for (i = 0, sector = sectors; i < numsectors; i++, sector++)
 	{
-		sector->lines = Z_Calloc(sector->linecount * sizeof(line_t*), PU_LEVEL, NULL);
+		if (sector->linecount == 0) // no lines found?
+		{
+			sector->lines = NULL;
+			CONS_Debug(DBG_SETUP, "P_GroupLines: sector %d has no lines\n", i);
+		}
+		else
+		{
+			sector->lines = Z_Calloc(sector->linecount * sizeof(line_t*), PU_LEVEL, NULL);
 
-		// zero the count, since we'll later use this to track how many we've recorded
-		sector->linecount = 0;
+			// zero the count, since we'll later use this to track how many we've recorded
+			sector->linecount = 0;
+		}
 	}
 
 	// iterate through lines, assigning them to sectors' linebuffers,
@@ -1952,11 +1960,14 @@ static void P_GroupLines(void)
 	{
 		M_ClearBox(bbox);
 
-		for (j = 0; j < sector->linecount; j++)
+		if (sector->linecount != 0)
 		{
-			li = sector->lines[j];
-			M_AddToBox(bbox, li->v1->x, li->v1->y);
-			M_AddToBox(bbox, li->v2->x, li->v2->y);
+			for (j = 0; j < sector->linecount; j++)
+			{
+				li = sector->lines[j];
+				M_AddToBox(bbox, li->v1->x, li->v1->y);
+				M_AddToBox(bbox, li->v2->x, li->v2->y);
+			}
 		}
 
 		// set the degenmobj_t to the middle of the bounding box
@@ -1966,6 +1977,35 @@ static void P_GroupLines(void)
 	}
 }
 
+//
+// P_LoadReject
+//
+// Detect if the REJECT lump is valid,
+// if not, rejectmatrix will be NULL
+static void P_LoadReject(lumpnum_t lumpnum)
+{
+	size_t count;
+	const char *lumpname = W_CheckNameForNum(lumpnum);
+
+	// Check if the lump exists, and if it's named "REJECT"
+	if (!lumpname || memcmp(lumpname, "REJECT\0\0", 8) != 0)
+	{
+		rejectmatrix = NULL;
+		CONS_Debug(DBG_SETUP, "P_LoadReject: No valid REJECT lump found\n");
+		return;
+	}
+
+	count = W_LumpLength(lumpnum);
+
+	if (!count) // zero length, someone probably used ZDBSP
+	{
+		rejectmatrix = NULL;
+		CONS_Debug(DBG_SETUP, "P_LoadReject: REJECT lump has size 0, will not be loaded\n");
+	}
+	else
+		rejectmatrix = W_CacheLumpNum(lumpnum, PU_LEVEL);
+}
+
 #if 0
 static char *levellumps[] =
 {
@@ -2574,7 +2614,7 @@ boolean P_SetupLevel(boolean skipprecip)
 	P_LoadSubsectors(lastloadedmaplumpnum + ML_SSECTORS);
 	P_LoadNodes(lastloadedmaplumpnum + ML_NODES);
 	P_LoadSegs(lastloadedmaplumpnum + ML_SEGS);
-	rejectmatrix = W_CacheLumpNum(lastloadedmaplumpnum + ML_REJECT, PU_LEVEL);
+	P_LoadReject(lastloadedmaplumpnum + ML_REJECT);
 	P_GroupLines();
 
 	numdmstarts = numredctfstarts = numbluectfstarts = 0;
diff --git a/src/p_sight.c b/src/p_sight.c
index 14c1c945f..bd6ab4d73 100644
--- a/src/p_sight.c
+++ b/src/p_sight.c
@@ -325,9 +325,12 @@ boolean P_CheckSight(mobj_t *t1, mobj_t *t2)
 	s2 = t2->subsector->sector;
 	pnum = (s1-sectors)*numsectors + (s2-sectors);
 
-	// Check in REJECT table.
-	if (rejectmatrix[pnum>>3] & (1 << (pnum&7))) // can't possibly be connected
-		return false;
+	if (rejectmatrix != NULL)
+	{
+		// Check in REJECT table.
+		if (rejectmatrix[pnum>>3] & (1 << (pnum&7))) // can't possibly be connected
+			return false;
+	}
 
 	// killough 11/98: shortcut for melee situations
 	// same subsector? obviously visible
diff --git a/src/r_segs.c b/src/r_segs.c
index ec3eaa180..59b4f5db9 100644
--- a/src/r_segs.c
+++ b/src/r_segs.c
@@ -1883,12 +1883,13 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 		// a single sided line is terminal, so it must mark ends
 		markfloor = markceiling = true;
 #ifdef ESLOPE
-		if (!(linedef->flags & ML_EFFECT1)) {
+		if (linedef->flags & ML_EFFECT2) {
 			if (linedef->flags & ML_DONTPEGBOTTOM)
 				rw_midtexturemid = frontsector->floorheight + textureheight[sidedef->midtexture] - viewz;
 			else
-				rw_midtexturemid = frontsector->ceilingheight;
+				rw_midtexturemid = frontsector->ceilingheight - viewz;
 		}
+		else
 #endif
 		if (linedef->flags & ML_DONTPEGBOTTOM)
 		{
@@ -2507,6 +2508,15 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 #ifdef ESLOPE
 			maskedtextureheight = ds_p->maskedtextureheight; // note to red, this == &(ds_p->maskedtextureheight[0])
 
+#ifdef POLYOBJECTS
+			if (curline->polyseg) { // use REAL front and back floors please, so midtexture rendering isn't mucked up
+				rw_midtextureslide = rw_midtexturebackslide = 0;
+				if (!!(linedef->flags & ML_DONTPEGBOTTOM) ^ !!(linedef->flags & ML_EFFECT3))
+					rw_midtexturemid = rw_midtextureback = max(curline->frontsector->floorheight, curline->backsector->floorheight) - viewz;
+				else
+					rw_midtexturemid = rw_midtextureback = min(curline->frontsector->ceilingheight, curline->backsector->ceilingheight) - viewz;
+			} else
+#endif
 			// Set midtexture starting height
 			if (linedef->flags & ML_EFFECT2) { // Ignore slopes when texturing
 				rw_midtextureslide = rw_midtexturebackslide = 0;