FWIW-- I have had exactly the same issue with Kirkland 312s – multiple packs over a period of time, so not " a bad batch. "
Sometimes they install at less than 100%. Sometimes they drain to a low level in a day. Sometimes they die within hours or even immediately. Sometimes they die slowly so I get warning chimes. Sometimes they die suddenly with no warning. And this can happen even if I’m not streaming or doing anything intensive If I put in a new battery it of course might do the same thing so I don’t dare to go out without a full pack of batteries.
I initially thought they were terrific – great price, and they lasted much longer than any other brand. So the comment that they changed providers interests me. I have thought about having my HAs checked out (Oticon OPN) but was deterred by covid closure.
I’ll try some other brands but am not sure that will prove if it’s the HAs or the Kirklands as the problem is completely in consistent in its manifestations.