In an earlier post I discussed having to rework my hatches because the fasteners on the hinge side are countersunk so deeply that the flange holds salt water and the screws corroded away resulting in a leak. I fixed that by filling the original holes with chopped fibreglass and resin up to the surface of the flange (Bondo or other fillers like JB Weld might work) then redrilling and countersinking only enough to put the head below the surface.
On one, one hinge pin fell out of place. Fortunately, the hatch did not break when I opened it. The design relies on staking on the pin itself to "grab" the plastic frame and hold the pin in place. It is obviously not 100% effective. I fixed that by pushing the pin back in place and putting gobs of epoxy resin on the ends. Those pins will not move again. If it is ever necessary, I will face that with a Dremel tool in one hand and my wallet in the other. If worse comes to worse, I will replace the hatch then. For now, my 50 cents worth of epoxy seems to be as good.
I also discovered that several of the screws which hold the thinner flange of the hatch in place had been put in so tight that they pulled through the plastic and were holding nothing. Also several were never installed in the first place.
This all says the design of the hatches and the installation at the factory both have some problems. If one has leaks, it may not be the hatch per se, but may be the installation. It would pay all owners to check the fasteners. Better to prevent a leak than to mop it up.
Hint: I discovered 15 minutes too late that I could remove the hatch without removing the interior piece. On our R21-EC, at least, it is strictly a trim item and does not connect to the exterior part.