Segway E22 sudden power failure

Got an e22 that’s been okay for a couple years of light use. 300ish miles. No major changes. No firmware updates preceding the behavior.

Charging is wonky and it will go from 10% to 80% in 15 minutes then refuse to charge beyond.

Riding it results in a sudden loss of power, followed by full shutdown into a free spin.

Battery, or controller? Is it even worth my time? I’ve read they’re awful to get apart.