Ya know....every device I have with a rechargeable battery eventually loses its ability to retain 'like new' charge capabilities.

HOWEVER...OP says one is brand new. And it does the same thing. Hmmm

www.newtis.info, prolly find a description for how they generally work

https://www.newtis.info/tisv2/a/en/e...system/XMWfMsG

https://www.newtis.info/tisv2/a/en/e...minals/XnGFECK

Anything of note around this "new" key??? Any programming done? any stories there?

JBE and FRMs can flake out and cause issues. Do you have ANY other electrical anomalies?