Can't say I recall ever seeing this bug on the original Doom 3 but shortly after getting the shotgun, there is one part where a imp crawls up next to a explosive barrel, just past that is a scripted event where a bunch of debree falls down from above. one of the objects landed on the stairs I needed to climb forcing me to jump onto said object, and I immediately became stuck. Couldn't jump, couldnt crouch, couldnt sprint, tried all directions with said key combinations , moved onto punching shooting with the pistol and shotgun to see if the object beneath me would move but to no avail forcing a reload to the previous autosave. (Which was way back right after you kill your first possessed and possessed soldier)

I would say the obvious answer is 'dont jump on scripted objects' but that one blocked the stairs so if it happens to anyone else, or again, not sure its possible to progress long as it continues. (I closed the game in annoyance but if it happens next time i'll try jumping onto the railing of the stairs see if I can scoot past it)

There are a couple of spots in the game that suffer from shoddy collision detection and where you can get stuck, although it's rarely an issue. (The only one that immediately springs to mind is a suit of armor in the Delta Labs, about halfway through the game, that's wedged right up against a lumpy mass of flesh and bone, where you can get jammed up.) I think you're describing a part of the old communications station where some steel girders fall down from above and block the stairway leading up. The physics engine is designed to let stuff get thrown around (this is actually a game mechanic in some levels), and moveable objects tend to be kind of "wiggly" and unstable; you'd have better luck running up the railing, as it's a fixed object.

Also, make frequent use of quick save (F5) and quick load (F9) to avoid getting dumped back to earlier in the level, especially if you think you'll be running into trouble.