This is a weird one. Sometimes, when my Rogue climbs some walls or mountain cliffs, he gets stuck right before he should be on the mountain trail.
It appears as if my companion is blocking his way, right before he gets to the top. When that happens, I can only go back down and try to climb again or I have to teleport away.
None of my other character ever got stuck this way or females are just the better climbers I guess.