Yo
Bit of a weird one as this issue has already been resolved, but I thought I'd make a post here about it as the guy at Apple had never seen it before and there was almost zero info online about a similar thing.
I've had my iPhone SE for ~6mo and it's done this thing a couple times now. It will stop showing a battery charge percentage but show a low battery, and then it will bootloop once every 10 mins or so. Extremely annoying. It has sorted itself out each time but it wasn't doing it this time.
Took it to Apple, the bloke was very confused and asked if I'd put an aftermarket battery in (which I hadn't). He believed me but said that the issue should be theoretically impossible with the original parts, and he had never seen it before. Long story short, he wanted to send it for testing, I asked for a spare phone in the meantime (iPhone XR with 64gb storage… how can y'all live without the home button and at least 128gb!?). A couple days later I got a notification saying that my phone had been "replaced" and further instructions would follow.
So anyway, point of this post is:
a) PSA if you ever spot something similar, and for something to show up in google lol, and
b) Anyone got any theories as to wtf happened? I highly doubt they'll explain it to me, knowing apple. I haven't done anything weird with the device but if maybe a charger or mine or something is buggering it, don't want that to happen again.
C'mon now. Apple makes tens of millions of devices with an internal battery each year and don't tell me that it's impossible to produce a single dud battery!
Once you start using an iPhone without a home button you will get used to it after a few weeks.
Can't live with less than 128GB? Personally I always use 32GB or 64GB. I rather save that $80/$160 and spend some time backing up my files when it becomes full.