NOTE: The full game is releasing in about 12 hours.
I've tried so hard to get this glitch to trigger, but couldn't. But everyone's feedback seems to point to it starting at a point in time where Nyari should use her ultimate attack, but doesn't, specifically when being stunned into a wall, at which point she should normally cancel into that ult.
It seems that the ult condition kept resetting itself because she was trying to go into the attack, but wasn't being registered as being in the attack, so it kept putting her back in again in a loop. But again, it's super strange how random the odds of this occurring were, as every time I tested, she'd recover from that knockback.
Sorry for the delay. Hopefully this change to the code does indeed fix that issue! And you ideally won't be seeing it in the full game, either!