I got the BMS_a066 recently with 88k km on my 2021 Model Y LR and booked an SC appointment. I lost about 80km range with the error.
The Service Centre ran battery balancing for about 18 hours in the hope that was a bad balancing or a software glitch, but today they concluded, that the HV pack needs to be replaced.
I am outside Toronto, they say it is running 2-4 weeks for shipping HV replacement packs currently.
They got me a loaner car (2018 M3). They feel it is best to not drive the car with the battery issue and drained the battery to about 150km.
I have not got an estimate, but assume it will be mostly covered under the HV Battery warranty.
Here is the history of the battery and with the big drop at the end.
View attachment 967379