Others have mentioned this, but I hope people keep posting about it now and then and keep bringing it up until CDPR acknowledges it: After killing an archgriffin (or some other events, though the oxenfurt forest one is the main cause), Geralt may no longer be able to climb walls, ever. If this happens, you cannot finish the game. You're done.

As always a simple reload would fix the issue if you haven't done it yet.

There are definitely certain ledges that you can't climb. But most is climbable, unless you are experiencing a strange bug.

I did have a bug with my beard growing wrongly, after reinstalling the game without using Galaxy, it went away. So you may want to try that.

Reload the game. Worked for me :)