time.monotonic() runs faster than realtime for Adafruit Metro M7 Express under CP 9.2.1

[twrackers]

I discovered that when a Metro M4 and Metro M7 are running the same code which acts upon a fixed period of time passing (measured by calls to time.monotonic()), my newly purchased M7 claims the time period has completed in only ~85% of the real time required by the M4. Both are sending begin and end messages via serial to a Raspberry Pi 400 which is listening to the serial via another Python code which measures the elapsed times. The Metro M4, as well as a Trinket M0, Gemma M0, and Circuit Playground Express, all come within 1% of the expected time.

Full details can be found in my forum post at https://forums.adafruit.com/viewtopic.php?p=1039811. The test procedure I used, as well as results, are posted there as well.

[twrackers]

Don't know if this is a clue, but the actual runtime was closer to 83% of what was expected, which is very close to 5/6. Maybe some counter or prescaler is specified incorrectly.

UPDATE: Actually a bit more than 5/6 with further testing. Hopefully I didn't just happen to get a defective M7 somehow. Waiting for further word on this.