Roof leak

[spence]

Our master bathroom has developed a leak at the vent fan which is installed in the ceiling and vents straight up through the roof. It's a vaulted ceiling with a *very* gentle pitch. Asphalt shingle roof with a pretty standard steel roof cap tied into the shingles and secured with two roofing nails in the holes at the bottom. I did it myself 10+ years ago and no issues until now.

Upon inspection I noticed one of the nails was lose and the bottom edge of the roof cap had warped up a bit. I pushed it back down and sealed the bottom edge with black sealant.

Still leaking.

Granted, the water could always be coming in from somewhere else. But would there be harm in screwing the bottom edge down (gently) with a good dose of sealant underneath, or should I think about reinstalling a new cap? Other ideas?