When I first started kegging I didn't realize they were different sizes. I eventually had half my kegs assembled one way and half the other.
This resulted in much confusion until I figured out my error.
Wasn't able to feel; broke apart too easily.
I think it was acetobacter, as the mead is lightly tart, reminiscent of a Berliner weisse. I threw in some potassium metabisulphate, as I had it on hand. I can grab something else tomorrow if that would work better.
I've been brewing for a few years and haven't had an infected batch yet. I did a low gravity (1.040 or so) mead which was fermented in a covered bucket with SA-05 and WLP720. It is down to 1.004.
I'm seeing a pellicle of some kind on the mead's surface. Does anyone recognize what this might be?