04 Tahoe overhead screen feedback problem

we recently installed an Initial brand overhead flipdown screen in a 04 tahoe. install went great just as always, until we backed it out of the shop. i left it running so the customer could get in and go and as i got out and shut the door, i heard this loud buzzing feedback type sound that only lasted for a couple of seconds. come to find out, the fade away domelights were the cause of the problem. when the lights went off the noise stopped. i opened the door to make the domelights come back on and then shut the door. loud buzzing again. the domelights on the overhead unit itself flash rapidly during the buzzing. when the buzzing stops so does the flashing lights. i've tried everything i can think of with no luck for a fix. i tried relays, diodes, you name it. the only thing i haven't tried is grabing all four door triggers and diode isolate each and use that for a domelight trigger. the customer was getting tired of waiting so they're coming back in saturday for me to fix it. any help or thoughts or ideas would great. this is the first time i've ever run into this problem and its got me stumped. thanks for any help.