I now make a practice to install LED side, brake, stop, signal, tag, and backup lights because of the intermittent problems you describe.
It becomes an SOP just to save time so you can work on other things instead of fixing faulty lights.
Uncle "Richard" Douglas has a Land Rover with big wheels that never gets stuck... until he breaks something so it won't go. Uncle Douglas always breaks something. - Anna Crowther at the Conclave 2012 (AKA Carburetor Neck)