Some background information: I have already tried running with no addons other than the required doom addons and get the same problems.
It really starts in the first map for Doom 2, if I back up to grab the chainsaw as usual, if I run into the fencing back there I will slip right through. Same thing happens where if you go into the big room, the fencing holding the imp in also has no collisions, so he walks right through it. Not a "game breaking bug," but definitely an annoyance at times.
Now the real issue starts with trying to move through the map. There seems to be some issues regarding the height of the playermodel or maybe even collisions with certain parts of the map. I tried changing my playermodel, using the Doom Marine through the doom menu, disabled all my addons except the necessary ones for this, and I cannot seem to figure out what the problem is here. Namely the Exit sign in the first Doom 2 map blocks me from actually getting inside the exit room, so I end up needing to use noclip.
Any help would be nice as I'm at a loss.