What causes screws to back out-- to unscrew themselves-- from gutter hangers? About 6 years after installation, almost all the screws had loosened appreciably. Just as if they had been backed out with nut driver. They were not stripped in the wood. I applied Gorilla glue and tightened the screws, but they have backed out again within 4 years. .
Aluminum one-piece gutters, aluminum hangers and zinc plated screws. I know about electrolysis, but this is what all the installers use.
What is causing rotation of these screws?