- recalculate the line deltas if a nodebuild is needed

One potential cause is moving around vertices in which case these do not match anymore

src/maploader/maploader.cpp

@@ -3105,6 +3105,11 @@ void MapLoader::LoadLevel(MapData *map, const char *lumpname, int position)
 	if (ForceNodeBuild)
 	{
 		BuildGLNodes = true;
+		// In case the compatibility handler made changes to the map's layout
+		for(auto &line : Level->lines)
+		{
+			line.AdjustLine();
+		}
 
 		startTime = I_msTime();
 		TArray<FNodeBuilder::FPolyStart> polyspots, anchors;