Headlight problems

my son has a 2003 chevy tahoe or trailblazer??? the low beams go out and won’t come back on until the car sits for an hour or two. the high beams work fine and the car runs fine, just the low beams go out. the chevy house replaced bulbs, a switch, and some sort of wiring, but say they can’t find the problem and say there is no service bulletin on this. driving with high beams is dangerous and the other people and police don’t like it. can you please help me??? thanks

Perhaps the low beam relay is overheating and shutting off. Has anyone tried a new relay?