After installing a new ifixit battery onto my iPhone8, it worked fine for a couple of weeks,
[image|3128876]
but this week it started crashing after the battery dropped below 80%, and in some cases even crashed when just trying to make a call. As you can see from the battery health graph, the charge plummeted suddenly from 80% to <10% when I tried to make a call. Seems like a severe internal resistance problem, since it cannot handle a heavy electrical load. Or a wacky BMS problem. I wiped and reinstalled the iOS and it did not help.