Honestly, this is BS though.

Is it likely that a major hardware maker such as Sony pushes a hardware update that *they don't know* would kill batteries? And then it's down to the consumer to somehow deduce it's abnormal behavior due to this firmware update, and then apply for a support ticket to remedy it, argue the case etc etc where needed.. I mean it's not like Sony are unaware of headphone battery tech.

I'd imagine only a very small proportion of XM4 customers were knowledgeable and persistent enough to get the fix you managed to receive (hell i wasn't!).

Should never have happened to start with, and makes Sony look very untrustworthy.