Hmm, that's weird. But AFAIR, the game is controller centric, so your character moves relative to the camera. Therefore, you need to keep the camera straight while moving on walls. If you move the camera, the character will move in that direction and even jump off.
Didn't have any issues with AC:Brotherhood. And Brotherhood is the best AC game as well. It has very simple combat, you just wait for the enemy to attack and perform an attack at that moment and he's dead. Climbing mechanics is also the best compared to any game. And I played with a KB/M. The only issue I had with AC games is that it locks the camera at some points in linear sections. But that is very rare.