We need to get the info from BambuLab if they want us to format any microSD card with the system’s format utility, always before use. FAT32 partitions can theoretically be as large as 8TB, but Microsoft has artificially limited the FAT32 partition size to 32GB in the past to promote its NTFS file system. So the Windows FAT32 formatting facility did in the past limit the volume size to 32GB. Windows 11 (10?) might not have this limitation anymore. I don’t know about Linux. exFAT was released by Microsoft to allow creation of files larger than 4GB in the file system compared to the 4GB limitation of FAT32. That’s for Windows Format. Does the BambuLab formatter use FAT32 or exFAT? There is no selection in the menu so I assume it’s FAT32. Windows 11 tells me that a FAT32 64GB SD card has a 62.4GB capacity and it’s a FAT32 file system after formatting with the X1C. Looks like 62.4GB should be available to the X1C, but with the 4GB file size limitation, right? Or? That would mean that you could run into file size limitations for time lapse videos for really long prints?
But all this doesn’t seem to impact the failure problem observed. So my conclusion is that there is either corruption during write access, during removal when the printer is still turned on and in the process of accessing the card or just a failure of the card itself. Also during the shut down process of the printer, files could be left open, i.e. corrupted, which would be the fault of the BambuLab firmware.
It doesn’t seem to happen often since there are not that many reports on it. Another thing to avoid, probably, should be viewing the sd card contents on a machine other than the printer. Windows always tells me when I do this that the sd card has errors and needs to be scanned and fixed. So I will avoid this in the future. Too bad and I will not be able to watch the silly timelapse videos on my computer anymore.