Thanks, Pie.
The problem might be resolved. Once again, this morning I went over all the basic things and found nothing of consequence. So I set up to watch the drive's LVIB (specifically the U30, UDX, and the UDX LED).

200 runs later, there were no anomalies, so I turned the car loose. It's at 306 uneventful runs as I type this.

I didn't disable brake monitoring, as I didn't figure out the secret key codes until just now.

Gonna watch it some more.