Couple of possibilities why you saw that.....

The hinge failed to hold the CA. Dubro hinges used to do that and they put holes though the flats so the glue would make "rivets" from the wood on one side to the wood on the other. Then the hinge could let go of the glue or not and would still hold thanks to the glue pinning the wing together through the holes. And back then, some of those type hinges were shiney. They didn't hold the glue worth spit from the gitgo. They're no longer sold. And Dubros now seem to be a plastic that doesn't continue to bleed solvent.

Lot's of CA hinges don't get rock hard when CA'd. Especially if you flex them during the installation. Technique is important doing any job.

All CA hinges are not equal. Just like all brands of anything aren't equal. We used to learn how to select balsa and reject the bad stuff. We also learned which flat hinges were going to let go of the epoxy (their plastic bled solvents that separated the epoxy from the plastic over time) and quit buying them.

Right now, I won't use a CA hinge that has no "fuzzy" on both sides. I also test all of the rest to see how well the fuzzy is attached. Never had a hinge fail since doing that. Also never ever had one that hardened. Flexing during installation might be the trick. You can do it before inserting, but should do it as the CA is setting up if only to keep the hinge supple.