I can't completely answer your question in that I don't know about the cables being individually replaceable, or if they are all on 1 single cable. Plus, I doubt it's the cable.
What you might check is the actual surface the post mounts to, in the roof of the PUP. I say this because ours is weak there, very weak, and needs to be repaired / replaced. I noticed our drivers side rear brace has some play, and that's the reason for it.
Might actually see if that's your problem, and not the cable lift system.
Greg, Janelle, Tenley, & Ellis
2019 Palomino Puma QBSS
TV: 2015 Silverado Z71
Other toys: 2007 Rinker Captiva w/Monster tower & rack