Try this, hot jeep, jack it up so the wheels are off the ground.
Start it up and put it in reverse.DO NOT APPLY THE BRAKES! See if it stalls.
If it doesn't,Now try it with the brakes ON, and see if it stalls then when put into reverse.
If it does, I'd say most likely you have a harness that's rubbing on something and shorting out.
With the wheels off the ground, the torque on the mounts and such is less, as all they have to do is spin the wheels.
On the ground or with the brakes on , every thing now has to torque hard over to get the jeep moving.
You could have a harness that once it gets hot it droops a tiny bit, and then when the drive train torques in one direction it touches a rubbed through wire and grounds it out.
I had an S-10 do exactly this. Ran perfect cold, soon as it got warmed up put it into reverse and it would die. Found a power wire to the smog pump ran right above the exhaust manifold, soon as it got hot the wire would droop down, and when put into reverse it would touch the manifold. That wire was on the same circuit as the ECM.
Ground out and would shut down the ECM.