Nothing, yet I was going to make sure that your device doesn't flash firmwares anymore, which is not recoverable as far as I know, but it seems that it still can.

Let's try clearing non-volatile memory, it helps frequently.
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Put Garmin folder on an SD card and insert it into the device. Then flash the RGN. And after, say 5 minutes, remove the SD card and upload its contents. A few new files should appear on the SD card. If there are no new files then don't upload

Also let's see how it behaves with the following tool:
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