Character is stuck between a cliff and a hard place (tree)

[jorb]

Perhaps, but, as stated, the problem being that that would imply that ridges can be blocked, which could be problematic in its own right, for example by creating fortresses on hills that cannot be reached.

[MagicManICT]

Well, we do have catapults now to siege such a design. Whether walls should be allowed to place that close could be a design decision.

Looking at the image a second time, it does appear that instead of moving down the cliff in the "cliff walk" position, they tried to move around the stump, or at least clicked so that the character was moved away from the cliff, so maybe there's a solution in there.