First post - Welcome to JF
One of the first things I would do is load test the battery. KJ's do some really weird things if they are not getting full voltage. Owners have reported the rear door clicking as one of the results of this.
Well worth checking. Not saying this is the only possible culprit, but a good place to start. Good to clean all battery connections too.
PS: You did not fill out your Jeeps profile - so we have no idea as to what year KJ you have.
05 TJ RME 42RLE with some things
05 KJ CRD 545RFE, GDE Eco tune, Franky II, Al's 4.5 A-arms, JK Rubi Moabs, Silent Armors 245-70-17's, Spidertrax Adapters, Rola Basket, Fumoto Valve, Pinch welds pounded
FS or FT (2) JK Rubi 17" Moab Rims - really nice shape
Need JK Rear Spare tire bracket for project