I play a super friends deck with her and also noticed this bug seems to cause the ability to stack until someone attacks you. Then all instances of the ability proc causing the creature to get multiple -1-1 counters

Tasha's +1 ability lasted several turns after she wasn't on board. I thought it was a visual bug two turns after the +1 was applied and my creature died as it was a 1/1.

To elaborate on one scenario I just faced, I removed Tasha with a Skyclave apparition, the ability did not phase out at start of opponents next round. 2 or 3 rounds later, thinking it was just a visual glitch, I attacked.... but then I still got those stupid negative counters.
Dunno what happened with testing for this last update but this place is coming apart at the seems, it's unheard of for me to notice two glitches in a release... (Mothrider is the next I'm reporting)

Tasha -1/-1 is definitely stacking and doesn’t resolve at the end of turn. It gains each time you +1

Same thing happened to me this morning playing with tasha in a game.