Loud vibrating sound on starting after replacement of a headlight

I had a fender bender on the front passenger side corner and the mechanic replaced the bumper, fender, and the headlight (the latter with a non-original headlight). After the repair the car started emitting an occasional loud vibrating noise when starting the car or stopping for longer than a minute (though it does not happen always but only occasionally and only when the car is warm and the headlights are on). It lasts for a few seconds and comes directly from the area around the new headlight. The technician traced the issue to a connection between the light and the car, but as far as I can tell he has not repaired many Priuses and can not figure out how to fix the problem. The connection is not obviously loose. I have an mp3 recording of the sound, but I am not sure how to post it. Has anyone had a similar problem? I have a 2008 Prius which never had any issues prior to this body work.