Mi Electric Scooter 1S suddenly won’t power on — battery issue or something else? (Error E7)

Hey everyone,
I’m having a pretty frustrating issue with my Mi Electric Scooter 1S and I’m hoping someone here has seen this before.

Two days ago I rode it to work with no problems and left it in the underground parking. When I came back, it wouldn’t power on. I figured maybe I forgot to turn it off and the battery drained, so I just walked home. On the way, it suddenly powered on by itself, worked for a bit, then shut off again even though the battery indicator was showing 4/5 bars.

When I got home, I thought maybe the display was faulty, so I plugged it in to charge. The next day it worked fine in the morning, but right before I got home it shut off again and refused to power back on. I assumed it was the cold, so I brought it inside and let it sit, but it still wouldn’t turn on until the next morning.

I checked the app and everything looked normal — battery level around 85%. I tried plugging it in again but the charger LED stayed solid green, as if the scooter was fully charged. I tried to power it up to check, and now it simply won’t turn on at all.

I’m about 90% sure it’s a battery issue, but when I tried doing a reset I got an E7 error, which from what I’ve read points to a failed throttle.
Has anyone dealt with this combination of symptoms before? Could E7 be triggered by a bad battery or BMS, or should I be looking somewhere else?

I don’t want to replace the battery only to find out the problem was something completely different.

Any advice or similar experiences would be super appreciated!