Airstream has been using that same bathroom vent for quite a few years now. We had a 2005 Safari 25FB and now have a 2015 Flying Cloud 25FB. Both had the same vents in the toilet room and shower.
Since the leak stopped after caulking, I would consider completely removing the old vent and checking for any distortions or damage that might be causing the problem. If everything looks good, I would try cleaning everything up and reinstalling with fresh caulk.
SuEllyn & Brian McCabe
WBCCI #3628 -- AIR #14872 -- TAC #FL-7
2015 FC 25' FB (Lucy) with HAHA
2005 Suburban 2500 Quadrasteer (Olivia) & 2011 Silverado 3500 (Fred) with Outfitter Truck Camper (Ethel)