Switch works. Motor runs. Passenger side of mechanism seems to be working OK. Drivers side both up and down seems to be dragged into position by passenger side. Have to help it up manually.
You would have to remove the back seat, rear trim panels, and possibly headliner to access and inspect all the components. I believe that the cables would be accessed by removing the head liner.
First thing you need to check is the hydraulic fluid level. Are there any obvious leaks? Remove drive motor filler plug. Fluid should be level with bottom of plug hole. If needed, refill with Mercon Multi-purpose ATF (XT-2-QDX). If it's low and you refill it, operate the system a few times to get the air out of it. If that doesn't correct the problem... post on. I'll deliver the next steps. Leaks and low fluid are most likely your problem.