easy earbud battery replacement

I just did a battery replacement on a Sony WF1000XM3 when batt life started decreasing from 8 hours to about 5, and the new batteries were giving problems. One lasted three days and then started obliterating all sound with a high pitched white noise sound. (the other one only worked for an hour or so each time before shutting down!)
I reported back to the seller (battery dealer in China) who refunded but then said he had never had any reports of failures in BOTH batteries at the same time before.
So I put the original batteries back in and the one that only worked for a few days and then started giving out a high pitched white noise-like sound now seems to give out no sound at all. It does flash its blue BT signal , it seems to disconnect and reconnect but there is no sound.
Does anyone have much of a handle on what might have happened during this exceptionally easy battery replacement? I'm pretty sure I didnt disturb any cables and anyway, the earbud DID work for a few days!
The Heisenberg effect?
Or must I now put it down to coincidental dying of the bud at the same time as I changed the battery?