2017 Freightliner cascadia trailer brakes smoking, not disengaging, caused by something to dotractor

Trying to help out my boss and the mechanic that will be looking at our truck figure out the issue. I pull double 28" trailers and just did about 2500 miles with my co driver ans everything was fine until we got a new set of 2 trailers. We got 10 miles from our hub and the brakes on all the trailers except the dolly were smoking. Tractor brakes are fine but me and my codriver think the issue resides in the tractor somewhere.

The same thing happened almost exactly about two weeks ago with our tractor and it supposedly was fixed when the brake pedal and some brake light sensors were replaced. Does anyone know what's wrong with the tractor? We are 100% sure it's the tractor causing the trailer brakes to engage and causing them to heat up. Tractor is a 2017 freightliner cascadia

 

unfortunately no.

yes we've checked that. Air pressure is going all the way to the second trailer at end too. We had taken it to Freightliner and they had worked on it for two weeks and if seemed fine on our trip to Orlando, Florida from industry, California.

 

me and my co driver drive for FedEx ground and we just had the mechanic there test all the brakes, slack adjustors, air lines, etc. This issue with the brakes heating up will happen regardless which trailers are connected. Something on our tractor is definitely causing this.

 

the mechanic at FedEx ground tested this and it was the first thing he checked.

 

abs light is coming on and going off repeatedly