Many paddlers with strippers put a coat of varnish on the inside of the cockpit - usually on the floor. UV does get in there and slowly breaks down the epoxy. It may only appear as a tiny pin hole that you can't see but eventually you get water infiltration as youÊhave. To sand the entire deck down seems a bit extreme. Why not live with it and let the cockpit dry out and give it a quick coat of varnish.