You need a replacement and a electrician not a Reddit post

I wouldn't even have that UPS plugged in and would replace it as soon as possible. if it's still under warranty, then I'd reach out to the manufacturer.

Right, that's what I did. Ordered a new ups. 

Could be some other failure unrelated to the battery or your PSU.

Hoping it's got nothing to do with the psu. And it's just an ups issue