My Father had that problem with his Crestliner for years. We lubricated those things with WD-40, grease, etc to try and make them less sticky but as others have indicated they just become stubborn over time. Plus them moisture gets in there too from rain, splash, etc which doesn’t help.
Eventually the bottom of the seat stems began to come apart too. He replaced the stems with a one-piece one instead (non-height adjustable) and the problem mostly went away.
I’ve got a Ranger with the turn/screw in ones and it much better than those slide/pop in ones.