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):
@lamefun 's work on improving the movement in general that has a relaship to this bug, so maybe he will be interested in taking it on .