Your gearbox is breaking due to your windmill spinning too fast. Putting a
block over the gearbox does nothing, but gearboxes do have a particular
reaction to receiving redstone power, you should experiment. ;) Redstone
power and mechanical power are designed to work hand-in-hand with a lot of
the late game automation.

Also, usually a gentle rain won’t cause the windmill problems, but those
storms… well that’s a little too much wind.