PS4 NA
I have never had this happen- but my mag, stam, & health dropped to a few % instantly tonight in Cyrodiil during combat.
1. I sit about 50k mag, 27k health, & 17k stam.
2. Not in a party, but 30 or so players fighting in view.
3. I had not been fighting long, 30s-1m, nothing intense yet.
One second I was fine, & the next all my resources dropped to 1-2%,of course killed right after.