Haven't heard much about this problem any more and not sure why, but originally hooking up a trailer harness usually would knock the magnetic brake switch out of commission. I replaced mine over a year ago and have never had an issue. If you want to or need to do this, this is how I did it.
First the bracket I made to mount the Napa plunder style brake switch (SL169. The plug has NAPA part # 725175). I used steel, but aluminum would work. Got a matching GM connector from Napa as well to plug into where the original switch did. No cutting and easy to swap back. Not to hard to figure out where to make the bend to catch the top end of the brake lever to make it work. Final step was larger heat shrink to protect the switch from any water that might be able to get to it. Have not had any problems with it in over 5000 miles.