I've tried everything. I've followed every instruction on the PCGamingWiki, I've tried RTSS, I've tried changing renderers from D3D to OpenGL like the good ol' days (I'm told). And no matter what I try, while everything else seems to work perfectly fine when capped at 60 or 58 FPS, the trucks in Hidden Valley STILL break things. I went down to 30 FPS and guards would still occasionally get run over. There's also this one glitch where, if I'm standing too close to this truck when it stops for inspection, the guard on the left will freeze in place and never move again unless I get his attention. This is an especially bad place for this to happen since I need to use that window of opportunity to sneak past the guards, which I can't do if they're frozen at certain angles.

Is this just reality? Is the level broken regardless of my framerate? If it is, I'll honestly be awash with relief that I no longer have to search for answers and can just work on finishing this really bad level. If there is an answer, feel free to let me know, I guess.

UPDATE:

Well. Took a short break and two hours later I beat the level. But only because I got lucky. That truck/guard got stuck again, but I managed to sneak past anyway and then walked all the way to the exit. I started the level over and ran at 30 FPS the entire time, and there was one early attempt where none of the usual stuff was breaking, before I messed up and had to start again. Maybe loading saves on any framerate messes up the timings? I don't know. I had issues even when i didn't save, pretty sure. Consider is still unsolved.