I noticed that too on mine. I ended up taking out all the screws, a couple at a time, squirting caulking in the holes, and replacing with stainless. Out of the 24 screws, 6 per bracket times 4, one was stripped, and 7 were broken. Drilling them out was not fun, and I own a machine shop! They go into an aluminum backing plate in the panel. You can see where they are when condensation forms on the outside wall. I know I didn't break them talking them out because the shear point was already rusted.
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