The simplistic explanation here is that Doom’s collision detection is basically all on a 2D plane. If you are firing a chain gun towards a wall, it will hit directly in front of you. If an enemy just happens to be on top of that wall and walks in front of you, the chain gun shots will hit them. It’s most noticed - and most annoying when it doesn’t work when you want it to - with rockets.
The simplistic explanation here is that Doom’s collision detection is basically all on a 2D plane. If you are firing a chain gun towards a wall, it will hit directly in front of you. If an enemy just happens to be on top of that wall and walks in front of you, the chain gun shots will hit them. It’s most noticed - and most annoying when it doesn’t work when you want it to - with rockets.