This is an old and annoying Tremulous bug. You can get wedged between a steep slope and another object so that you can’t jump out. you can usually slide back and forth (usually very slowly, although the current wall coasting does help with that), but if the ends are obtructed, nothing can be done (unless you are an alien that can wall walk, fly, or wall jump, or if you are a human with a jetpack). Many are probably familiar with this bug, here classic example (stuck on niveus between the barrels and the sloped wall):
I finally got a chance to port over your fix, it is on the GrangerLab server right now, and seems to be working great so far, but before I mark this issue as solved, lets see if there are any new side issues at the dev games later today.
Maybe there’s a ground check like in CheckJump, which I removed from it because CheckJump was only called from functions that themselves required you to be on the ground to be called, so the check was redundant.