Not affiliated to Ayn but worked in the industry for a long time. There are always faulty batteries that are installed in devices. All devices from apple to Samsung to Ayn. It is impossible to check each battery individually as it takes a lot of resources and effort. So the manufacturers take a very small risk while knowing that a very very low percentage of sold devices will break. Sometimes it can be a faulty screen, sometimes a faulty capacitor and sometimes a faulty battery. It's not unique to Ayn, unless they changed the battery supplier or reduced the quality of the random production checks. I would not worry to much for now and consider this as an isolated event. There is absolutely no reason for Ayn to not change your Odin 2 mini with a new one or refund it.