Another update on Scarlett: Without a software update, and with TeslaFi still enabled, my AP2 functions started working again yesterday, and have continued to do so for several consecutive short (10-20 km) drives. I did notice that the car seemed to be coming out of a sleep state when it began working again, that is, the IC was still booting up with the "T" logo when I opened the door to enter.
I have a long trip (~1,200 km) planned for tomorrow through Friday, so I am crossing my fingers that at least TACC remains functional! A lot of it is divided highway (Trans-Canada and Coquihalla), so this will be my first chance to try AP2 AutoSteer at full speed, IFF it has actually calibrated itself finally!
[forgot to press post on this last Tuesday, further update on the trip to follow...]