I would not normally post something like this, I’m only doing it because of the safety implications:
Watch :https://www.youtube.com/watch?v=dkiFG5SwZ6Q
Looks to be a battery originally manufactured in 2018; they did have a limited run of under-tightened internal bus bars back then.
…not that I trust them any more today, quite the opposite actually since they, like many manufacturers, have allowed themselves to fall prey to the same enshi… er, “platform decay”… that’s run rampant across the globe over the past few years, but still, this appears to be a very old issue that Will happened to notice just because he was working on an old battery.