I have not nailed down the mechanic causing it exactly, but I do know that in both instances, I had alcohol in a nearby chest in various glasses that DID decay to vinegar correctly, ie mead in several drinking horns, weibeer and beer in tankards, wine in wine glasses, etc. and they were confirmed to have been in that chest in cups for longer than 7 days. But the nearby alcohol in demijohns had not been there for at least 7 days. Something about the timers are being progressed for all of my nearby alcohols when alcohol in cups in a chest decays. maybe just mead? Edit: not just mead, took my wine too.
I believe that when the alcohol in the chest decayed from mead to vinegar, it also triggered the nearby demijohn to ALSO progress it's timer from mead straight to vinegar, several days in advance of when it should have.
In both cases, it was a demijohn of mead that decayed to vinegar with a drinking horn of mead that decayed in a chest(along with several other varieties of alcohol)
TLDR hypothesis; mead or mead must in a demijohn with a fresh 7 day timer will decay straight to vinegar if a drinking horn of mead inside of a chest decays to vinegar.
Edit: Just noticed another 2 demijohns of wine turned straight to vinegar. I didn't take a 10 day break. I've lost 250L of alcohol to this bug. And I just replanted all my grapes so I won't have wine for weeks.
