I just replaced motor on 6316, motor #524664, replaced by Lippert #368221,
https://store.lci1.com/gear-motor-wi...ue-368221.html.
It does have the brake as noted, it can be a pain to disengage. Likely you can remove motor. I believe you need to get your socket in there to crank it out at the motor, "while" someone pushes gently from inside.
Is it possible you have the manual slide lock/bars in place? I made that mistake.