Follow-up to my issue:
Two days later, all seems to be normal with the car (albeit all my previously saved settings are gone). When the issue occurred, I made a service appointment--the app decided I needed a SC visit, not a Ranger. First appointment, two weeks out, so I haven't been in a rush to cancel it, in case I have further issues.
Last night, I get the appointment acknowledgement, along with the estimated invoice.... for 1/2 hour "diagnostic charge." Uh, my car's under warranty. Even "if" this is more than a one-off software burp, why on earth would I expect to pay to have it addressed...??
Tesla. Love the car. The company...??