You have to much pressure on the brgs in the column. The shaft has to slide, and sometimes it doesn't slide enough, and puts pressure on the brgs in the column. You can remove the pinch bolt in the upper you joint and try to take pressure off the column, if it frees up then you know that's the problem. You can try tapping up on the shaft gently at the upper joint with a plastic mallet.
86 CJ7 5.7 vortec. 4L60,D44's,OBA,Air tank bumpers w/D rings detroits,4.88,35" bfg, mt's 9500ti warn
86 CJ7 2.5 detroits, OBA 4.56, air tank bumpers, w/D rings,9500I warn 31x10.5x15, Trxus
86 CJ7 bone stock, w/factory 44 never seen the dirt soon to be for sale
87 Wrangler also never seen the dirt.