Apple Watch Series 10 battery is draining fast after watchOS 26.0.2 update

Starting a day or so ago, with no change in my use or apps or anything else (I installed wOS26.0.2 the day it was available and all was well for several days), my AW Series 10 (it's about 10 months old) started using up its battery from 100% to almost 0 in four to five hours. Before this, the battery lasted 18-19 hours.

I've done everything recommended by Apple and the various 'influencers' ... I've turned off App updating, I've reset the website data, I've even unpaired my AW10 from my iPhone 16 Pro Max and repaired it (and spent ALL THAT TIME re-installing my credit cards and driver's license) and no change. I charged it to 65% 3 hours ago, and it's almost completely drained.

I did notice, in the diagnostic history, a couple of days ago, something called an OTA update. But, I didn't do that. It was done by Apple remotely.

This very same kind of thing happened last year, about this long after the AW10 was released, and I got tired of trying to fix my AW9, and traded it in.

[Re-Titled by Moderator]

Original Title: Apple Watch Series 10 - Battery Draining FAST! -- All of A Sudden.