Thanks for the information. I did follow the "Erase all user data" path on reboot several times but it hasn't triggered an upgrade.

I think flashing region 14 with 4.00 fw_all.bin is too risky. Next I'm going to see if putting a 17k resistor from ID pin to ground (to emulate a genuine Garmin charger) changes the boot sequence and triggers the update. If that doesn't do it, I'll just leave the firmware at 2.30 since it's fully functional.

Thanks again for all your help.