Apple Watch series 3 battery draining very fast, just started doing it

Since Monday 12/7 my series 3 watch which had previously stayed above 80% by end of day) has started draining the battery very fast. By 7 pm (after 13 hours of use ) is almost dead.

why?

it only wakes when I tap it

all the options are off including heart rate monitor that are normally suggested by users

i have power cycled it

i have re paired it

i have let it go dead and charged from 0%

I have installed no new software (except the most recent update)

it just started draining the battery

WiFi is also off

watch battery health says battery is at 100% capacity

it has been on for 3 hours and is already down to 78%

has it been issued a kill command to “encourage” me to buy a new watch ?

this is very frustrating to have this suddenly happen with no slow loss of capacity