Facepalm: In a case of something going from bad to worse, Humane, the maker of the critically panned Ai Pin, is now warning owners of the wearable device to stop using the included charging case as it may pose a fire risk.

Humane said in an email to Ai Pin buyers that they should "immediately" stop using the charging case that comes with the device following reports of a "charging issue." The company writes that the problem is a quality issue with the battery cell from a third-party vendor. It seems certain battery cells supplied by this organization pose a fire safety risk.

Humane emphasized in the email that it is looking for another supplier after "disqualifying" the vendor who supplied the battery cell. It added that the $700 Ai Pin device, the magnetic Battery Booster, and its charging pad are "not affected" by the issue.

To compensate for the problem, Humane is offering owners two free months of its subscription service. It normally costs $24 per month and is a requirement if you want to use all of the Ai Pin's functions.

Interestingly, or worryingly, for owners, Humane never mentioned anything about offering replacement charging cases. The firm only said it would share additional information after investigating the issue.

There was so much hype around the Ai Pin that Humane managed to raise $240 million from investors including OpenAI CEO Sam Altman. Last year, it was valued at $850 million by investors, though that was obviously before its first product arrived to a universal panning.

The Ai Pin's reviews ranged from "meh" to utterly scathing. In the latter camp was Tech tuber Marques Brownlee, who called it the worst product he's ever reviewed – a claim that led to an online debate over ethics and influence. It's reported that that Humane received about 10,000 orders for the device, most of which likely came from early adopters. Humane had hoped to ship 100,000 Ai Pins this year.

In May, it was reported that Humane was seeking a buyer willing to pay $750 million to $1 billion for the firm. That sounds like an optimistic price for a company that has released just one very unsuccessful product with a charger that can catch fire.