So it definitely can't overwrite either region 14 or region 127 which are for the main and supplementary firmware.

In that case either they're both really badly corrupted or there's indeed physical damage affecting both of them .... hmmmm, maybe a little coincidental that they'd both be so severely corrupted as to make overwriting impossible methinks. Regardless, let's try to dump copies of them so please follow this:

REMOVE last_id.bin from 0972 folder (or no further commands will be executed), also remove the 14.bin and 127.bin files from Garmin folder. Make a copy of 41.bin and remove it too. Check if it's size is 4 MB (4,194,304 bytes) and only if it's not that exact size upload a copy of it (compressed to a ZIP or RAR file).

Change the content of update.txt file to read only this:
Code:
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(If you copy/paste the above text make sure you don't have any extraneous spaces at line ends or carriage return below it).

Flash as before in preboot.

Good luck. Post copies of the BINs if they dump successfully.