2021 GMC AT4 trailer light issues

[allen sims]

I have a 2021 GMC AT4 2500 HD 6.6 Duramax. When I hook onto my 2021 travel trailer my clearance flicker and the come on but they are dim. I have a rear view camera on the back of the trailer that will not connect to monitor inside the truck. Everything on the trailer worked fine when it was connected to my old truck, a 2018 GMC Denali 2500 HD. I had a mobile RV mechanic come out because I assumed since the truck is only 2 weeks old it had to be an issue with the trailer. Checked the voltage to the camera and it was 11.8. Started looking for plug issues and found nothing. We connected the mechanics truck to the trailer and everything works perfect. Camera connects to the monitor and the clearance lights are nice and bright. To the truck to the dealer who ran a couple of test and says everything on the truck is working fine. I see some post on here say there is an update for the control module but my dealer says there isn't. Any advice or tips would be appreciated.

[EddDe]

This may not apply, but search for this bulletin: PIT5747 Diagnostic Tip - Trailer Lighting Complaints With Trailering App RPO U1D