Thanks for the reply’s
It ended up being the circuit board in the tail light assembly
I replaced both tail light assemblies and everything works like it should now
Couldn’t find anything wrong with the wiring
Father in laws 2002 Jeep Grand Cherokee
Brake lights work fine until you turn the running lights on and then only the brake light works at the top of rear door.
Turn the lights off and all brake lights work.
Any ideas?