You are making a very wise decision Ted! This would end up being filed under the category of no good deed goes unpunished.
The only other easy check would be to make sure the relay contacts are opening when it is pulled from the socket. It is rare but mechanical relays can fail in the closed position.
I taught several executive MBA courses in Queretaro which is near the GM truck plant. Over the years I saw a number of vehicle repairs that were definitely interesting. I saw another side of things when consulting for the National Insurance Crime Bureau and a number of vehicles that crossed the border as parts did so because of past export sales efforts that weren't backed up with a long term parts supply.
2018 2500HD 4X4 GMC Denali