Thank you for playing the game
After looking into it, issue is not physics related; that should already be time-stepped fixed properly, but rather a janky implementation of elevators and a handful of other map features which do things based on elapsed time. Elevator platforms are coded to move towards a point until its position lines up, but when the fps drops, it doesn't check position frequently enough until overshooting its destination.
Thank you for bringing this to my attention; i'll try and have it fixed in the next patch. As for the mouse issue, this is the first time I've heard of it and I'll have to look into it.