Yeah I've never assigned any specific functions to any of the actions in Custom Controls. With the exception of 2 functions in the RHS options that wouldn't work otherwise. Some of them are pre-set by default. Like if you assign a key to action 2, pressing that key will bring up a weird radial style menu where you can select between different weapons you're carrying. Action 1 is enhanced movement. Action 3 is a jump. I don't know about the rest of them because nothing apparent happens when I've tried them.
My guess is that whichever action you had set to be the climb in ACE options probably had another script attached to it, which then overrode the climb command you were trying to use.
Glad you got it fixed!