I am having a very similar issue. Battery % drops 2-5% almost instantly. Usually in the 59%-65% range. This happens at home, while plugged in (in a garage and sentry mode deactivated). Eg. I returned from a drive and parked at 64%. Plugged in the car (sentry off). A few minutes later, battery is at 61%. I’ve seen the drop as much as 5%, in one case.
Also, I’ve seen the vehicle report higher than the charging limit after overnight charging. Eg. charging limit set to 70%. Car charges and sends notification of reaching charging limit overnight. When I check in the morning, charge is at 73%.
I use Tessie as a 3rd party app to monitor details of my driving habits and battery performance. App is set NOT to wake the car every time I open it. Been using it since delivery in FEB 22. Symptoms described above only started in August.
Tesla has done some remote diagnosis, but came up with nothing. Any ideas?