has anybody else had problems with their rear bumpers splitting by the corner of the rear fender next to the taillights

 

NO

 

Splitting? Mine had such a close gap (at the corners where the tail lamp assembly, rear 1/4 panel, and bumper meet) that the vibration/flex wore through to the urethane under the rear fascia. They loosened up the bumper and put it back..touched up the worn spots with paint.

Define splitting. Do you mean that the bumper is flared out from the 1/4 panel a little bit at the corners? If so, just give it a little whack, but don't miss and hit the steel.