Sorry I'm late to the party, but, did you check the stamped steel locking ring on the shifter. This happens so often with mine a carry a spare. I think I've figured out my problem. I think the shifter has been bent by someone manhandling it when going into reverse. I think the stick hits the openning in the locking ring and bends the ears causing the shifter to not work. Right now the trans in out, but when it goes back in I'll know if I'm right. It sounds like you may have the same problem.
Your picture shows the locking ring on the shifter. Are the ears bent?
1985 CJ7 - total customization underway, Sublime green and Plum crazy purple, Ford 9", 258 w/ Holley 475
1985,93 CJ7,YJ - L98 TPI Vette motor, Atlas twin stick, Dana 60s front and rear, Arbs, 39.5 Swampers