Frog Song Glitch In Besieged?

Encountered a weird issue today when I was frog charmed in Besieged. I had over 1800 HP with a Giant's Drink, so I was not fully healed.
When the charm ended and the costume was removed, I was in a state of KO, but my HP was the same. It was not on zero.

I have never seen a KO before while my HP wasn't zero, nor have I ever been KO'd from a charm effect.
I didn't have Reraise, so I had to blood warp and return. Has anyone else encountered this?