I recently had a leak behind the diverter in my shower/tub. After replacing the diverter, the leak persists. This is leaking behind the flange that is closest to the threads on the diverter. Is there something in the plumbing in the wall that could have caused this? These are brass fittings, the house was built in 1976.

Thanks!!

Brand and model of valve would be helpful. Was the diverter kit an original part from the same manufacturer?