3rd gen interior lights flash when brake pedal pressed

Bought a brand new 2023 TacomaRD Off Road. Had a new Boss snow plow installed as soon as I picked up new truck. Now, after 1600 miles, I noticed that the interior lights do not function correctly. They will stay on if I have them set to door when I start the vehicle. The lights will shut off normally if I shut the vehicle off and shut the door. One of the map lights will not turn on unless I move the three way switch to on. Pushing the brake pedal will turn on the interior lights if i have the switch set to door. I brought the vehicle to the local Toyota dealer to have the lights checked. It took the service manager about 30 seconds to see the Boss plow wiring sticking out of the grill as the plow wasn't on. He stated, you added electrical items to this truck. Toyota states you can't install a plow and stated Toyota will not cover anything under warranty. I paid them $185.00 to tell me to remove the plow wiring and that the truck basically was not under warranty anymore. They stated that the map light and dome lights turning on when the brakes were depressed was a short caused by back feeding to a ground circuit but offered no solution. What should I look for. I am having Boss check the wiring they did. Only wire I found to the electrical panel was to a a fuse marked 10A ecu-ig no2, but they had added a second 10 amp fuse tap. Any help would be appreciated.
Update: Boss snow plow removed all wires from power source and grounds. Condition continues.
Update. 1-27-23. Toyota dealer did extensive trace of wiring. Plow wiring ok. Toyota tech. Found moisture in overhead council. No leaks found from windshiel d area. They believe overhead council( crawl control, etc.) Had been installed with moisture in it. Waiting for new overhead council.

 

Tacomas are notorious for weird electric issues whenever anything is added or modified that requires an electrical connection.
The issues likely rest with the installer of the plow not understanding how touchy Tacos can be.
Good luck!
BTW, welcome to TW.