Those wallered out holes from panels moving with the heat are exactly what I ran into, and it only gets worse the longer those panels sit in the sun. The fix you landed on is the right one, screw the flat every time and let the panel do its thing instead of fighting it at the rib. One thing I'd add is to check your fastener length against panel thickness, because a screw that's a touch too long won't clamp down flat and you get the same leak problem without even knowing it. Also run your screws in a straight line and keep the gasket snug, not crushed, since over tightening is just as bad as under tightening. The 20 extra minutes is nothing compared to tearing off panels to chase a leak you can't find. You're not crazy, you just figured it out before it cost you a callback.

Wow, six levels deep is Bad but was one comment really life changing?