Well, logical troubleshooting seems to point at the controller.
"Hopkins" is the brand they sell in Walmart, so likely it is not a very smart controller. Just a time-based controller.
What is the possibility of transferring the controller from the old truck?
A new controller would be <$100 and a good investment to get away from the basic Hopkins unit. Something like a Prodigy P2 maybe.
Putting 10-ply tires on half ton trucks since aught-four.