That one hasn't been reported before. The maps will be marginally bigger than what you had before but I suspect you picked one of the zones since all Europe won't fit on a 16gb card unless you start hacking it which isn't recommended.
The map is held on the map card in the mib2 standard so the data is dragged off the card and displayed. The only thing that can happen is the card is giving away. It does happen. You aren't suppose to play with the cluster size which is suppose to be at 4096. Too small and it thrashes around too big and it doesn't work. Windows 10/11 file manager did have a bug in one release or releases and succeeded in deleting the CID getting into areas it shouldn't if you did a reformat. Thus best to just do a delete and not treat the SD as a floppy / compact disk since a reformat with the wrong cluster size can lead to issues. You obviously need the workaround.
You can treat yourself to a new 32gb card Vag card off ebay, selecting a good seller. That way you'd get the all Europe map on and if the issue is down to a defective SD card it fixes it. You need the workaround and I have linked to the solution if you loose the overall.nds file.
You can also do the TMC Inrix fix if you haven't done that. That's linked in the
guide.