Check the seat switch wiring connectors for poor fir or corrosion.
There may be several connectors serving the seat switch harness on its way to the truck main harness and I have found that corrosion or a poor fit at any of the connectors can cause this.
A defective seat switch or switch operator bar/plate can give the same problem too.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.