I had it running the whole evening, with copying files to and from the SD card. Eventually I stopped when I went to bed. This morning, the SD card still is mounted, but empty, not readable, attempts to access it fail with error as observed earlier.
Finally, I unmounted the SD card and re-mounted it. I received the question whether I wanted to format it, I did so, and it failed at 20% again. So, the previous errors are back.
After another reboot, the card is back mounted, but it is not possible to write to it, etc.
Different brand, but similar specs. Have you tried formatting the SD card on a computer first before you format it on your phone? That worked for me. I also use the GPT partition table (but the MSDOS one worked fine as well). I formatted it to exFAT on my computer. At first try it didn’t work for me either, it was stuck at 80%. After formatting it on my computer first it works like a charm with stable performance.
Is it still empty when mounting it on a PC using the card adapter? I had the same effect with A.103, showing up all directories and files when mounted on machines running Linux resp. that other system…
Sounds like you’s be well off copying the contents for safety and reformatting the card. What formatting does it have currently ~ exFAT ?/
I use FAT32 for Windows 11, Android 11, Ubuntu, Raspberry Pi and all my 9 SD cards are moveable without a problem.
Still it could be useful to know what format you have on the ‘problem’ card and if you have a spare card you could try a different formatting to see if that works across devices.
I wouldn’t suggest using a FAT32 formatted card with the FP4! I had some rather problematic issues ( ) with files bigger than 4GB. Those shouldn’t be writable to FAT32 but the overlay filesystem makes this possible. Once the card is removed, that file will no longer be accessible and even putting the card back into the phone won’t make it recoverable again.
I think many had issues with SanDisk and bought a Samsung Evo instead…else looking at the wiki (after sharing ) it does not cover all experience, because interestingly not 1 SanDisk is documented under problematic…so indeed not that helpful
In the beginning, I suspected the FP of somehow corrupting the card’s file system during formatting which would have made it necessary to do a fresh format on a computer when giving it another try. Don’t know if this makes any sense but it seemed to help with my SanDisk together with the latest updates.
) with files bigger than 4GB. Those shouldn’t be writable to FAT32 but the overlay filesystem makes this possible. Once the card is removed, that file will no longer be accessible and even putting the card back into the phone won’t make it recoverable again.
Who in this topic is having problems with SanDisk cards and who experiences problems with another manufacturer? 
) it does not cover all experience, because interestingly not 1 SanDisk is documented under problematic…so indeed not that helpful
but thanks for the warning, which I ought to know 
I’ll reformat some for future proofing. Thanks.