I'm assuming what I just encountered was a bug but I'm not certain. I was doing Junon League Brawler Cup and the first enemy uses Obsession first turn. I was using Tifa and her health dropped from dual insanely fast, but when she hit 0, it said grit was triggered though she remained at 0 hp and now the battle appears to have soft locked. for several minutes, I have been at 0 hp, getting no turns, but still alive.The enemy keeps acting, but nothing kills me.
Edit: The dual effect finally ended after an extended period of time and now I'm at 0 hp but am not dying, and still getting turns, so it seems I'm unkillable in this scenario.