My camera came with the microphone not soldered at all (two microphone wires were hanging above the motherboard with no sign of soldering).
That was an easy repair as soon as I figured out what's the culprit, but before I've blamed the software for this issue for two days and tinkered with the software for at least 6 hours with no result.
adryjanowski, very nice tutorial, thank you!
I did. It's an indication of no free space left on the SD card.
It happened to me when I've freed up some space on the card using MacOS, but it actually put the files into the Trash folder on the card instead of completely removing them.
Formatting the card in the camera is the quickest solution if you don't have any valuable files on it. Else, insert the card into the computer and clear the Trash bin after the card is detected.