Hi everyone,

My Garmin Forerunner 645 Music has been stuck in a boot loop (blue Garmin triangle logo repeating endlessly) for a few days, most likely caused by the TopoActive 2026.10 map update.

What I've already tried:

Power off/on → no effect
Master reset (holding UP) → no beep/vibration, doesn't work
WebUpdater with recovery mode (holding UP + START while plugging USB) → device is recognized, but update fails with "corrupted file" error
Garmin Express → doesn't recognize the device
Garmin support → told me the model is no longer covered
Diagnosis from Garmin Express logs:
The device connects in GarminMode but reports Unit ID = 0. The exact error from the log:
GET .../unitids/0?primaryFirmwarePartNumber=006-B2888-00 → 400 "Unit ID is required"
This explains why WebUpdater rejects the firmware — it can't validate the device identity.

Device info:

Model: Forerunner 645 Music
Firmware part number: 006-B2888-00
USB VID/PID: VID_091E / PID_0003
OS: Windows 11
What I can do:

Hold UP + START to stay in recovery/preboot mode (I can tape the buttons)
Device is detected by Updater.exe in this mode
Would anyone have the RGN firmware file for this model and the correct HWID, so I can attempt a forced flash via Updater.exe? Any guidance appreciated.

Thank you!