Read this thread again and the 2 above links.
What is the 10 wood screws on each port biting into?
Fiberglass or the wood/plywood coring?
Tested all 60 screws on my tub today: 2 on each side is not biting, can be turned by hand. Pulled one out, no signs of wood fibers from coring, if anything, a bit of white caulk.
The lose ones were on the bottom forward side:
Have not taken anything apart yet: Caulked on the top and on the sides of each Port porthole as a temporary measure, could there also be water intrusion at the inner seam of the external face plate, where it meets the main body of the porthole?

If so, I have more caulking to do..
