Your hull looked to have a small rebate but maybe it's just the glue line. I noticed the extra length in the fabric, a bit strange that. You should need to pull really hard to get the strip to come away and you should feel that you may be risking tearing the PU surface away from the weave.
A rebate can be ground onto the flange and this will have the second advantage of preparing the fibreglass with no contamination, unless you put your greasy fingers all over it.
It only needs to be very slightly more than the fabric thickness.
The pictures you posted appear to show the adhesive still on both surfaces. Therefore, it implies that the joining together has failed rather than the adhesive to the hull and fabric has failed. When the two glued surfaces are brought together there should be no moisture present, not even from your breath. Certainly don't do it on a damp day or with the boat parked over wet ground or grass.