I'd first look at the tailgate assembly's bracket & reinforcement, see if their out of alignment.
I'd second look at the latch & striker assembly. The striker itself has plate, shim, and washer. Your shim may be gone. Plus check the striker cover (housing) for loosening.
Final 'guess. The pair of tailgate hinges are one piece design. You could shim the space between the hinge and the tailgate with something, then retighten the torx.
'90YJ Hard & Soft w/Full Drs; 4.2 Rebuild w/ Webber, 30x10.5; Interstate MegatronII D34; Mods: Rock Guards; Hi Lift Inst; Herc'd Tub, Front & Under; Elev Rear Seat; Scty CntrConsole/ Overhead&Rear Boxes; KC Lights-Fr & Rear; PA Sys; Gauges; Int Lts; Batt/Alt Cable; Heater Mods; 8K Winch, KargoMaster Rack w/Yak Megawarrior Basket; Ground Lights (4);Dumped - Optima Yellow after only 4yrs