Sounds like one of the cells has died; fully agree that it's best to replace the battery (given its 7th gen, I doubt it's still under warranty).

Alternatively, if you like tinkering with stuff just for the sake of it, you can replace the offending cell (often slightly expanded compared to the rest of them), or all 3/4 of them: in my experience, replacing only the dead one results in another one dying relatively soon after, but may still be a viable temporary solution if you're short on money or have something of similar size lying around. Also, if you decide it sounds fun, be sure to look up how-to's, as just disconnecting a cell will make most BMSes lock themselves + possibly burn the fuse, and you probably don't want to play the game of "is this BMS unlockable without paying 100500 kilomoney for specialized equipment"