I've seen such when the top folder gets too many files in it. There are limits to how many files are in the top folder and well discussed.
Here I don't see any mention of this or if you copied out the files, formatted the stick or card and tried to save a file there.
-> I would be guessing if you are trying to keep your files only on this card or stick. That is something that folk learn to be a bad idea.
This has happened to me more than once, the computer blocked me from saving my text files to a device. Last time it happened I mangled the thumb drive device, but it still worked. Not that it would let me write to it.
When I open the contents of this SD card it has a lock icon that is now showing a locked position, so I thought that would be the location of the problem. But it says is open to me to “read and write”, but maybe not to the 'open office'??
And what is even more odd is that it reads that the card is full. Well it wasn't full a very short time ago. I may have set the computer to use the card as a backup location. Like I did with another computer (some card). So are backup files invisible, that use up 12GBs or more?? and how can I clear them off the card if I can't see them?
maybe it is all because of the back-up filled the card?