Already did that several times, I'll do it again just for kicks.
Switching it for another unit also seems not a real solution as the problem is clearly in the software - like I said, the default 2.8 without FW upgrade is recognized, I can copy files from/to the device without issue. I haven't used or tinkered with it whatsoever either, this is straight from the box.
The second the upgrade to 3.12 is done, the device is not recognized anymore by windows, and the dreaded format prompt comes up. In fact, the drive is RAW, meaning that the partition is not even detected / chkdsk is a no-go.
I found threads with this issue dating back over 4 years ago, with no satisfactory fix.
https://www.mobileread.com/forums/sho...d.php?t=182819
https://www.mobileread.com/forums/showthread.php?t=98206
https://www.mobileread.com/forums/showthread.php?t=91406
https://www.mobileread.com/forums/sho...d.php?t=227463
https://www.mobileread.com/forums/sho...d.php?t=163257
https://www.mobileread.com/forums/sho...d.php?t=177591
...
It's hilarious a show-stopper like this remains unfixed for so long. It seems to me that the people at Kobo are complete amateurs with no QC or QA whatsoever.