I've had SCP 173 Spawn in my face at least twice. you may need to check on your spawns for 173

I'm guessing that single-sided polygonal collision detection in Blitz3D is causing this problem.

An easy fix would be to modify the rmesh loader so nothing can go through walls from the void.

It's not that, 173 Isn't no-clipping. It simply spawns next to me when I enter rooms sometimes.

173 moves so quickly that it looks like it teleports, so the single-sided collisions could be the issue. I'm not certain though, I'll take a look.

Edit: now that I think about it, it might be scripted spawning that's causing the issue.