Some more information. When I open the map in a terminal and try to remove the file main.py, I get the following message:
alfons@Sirdal:/media/alfons/CIRCUITPY$ rm main.py
rm: kan ‘main.py’ niet verwijderen: Bestandssysteem is alleen-lezen
(Cannot remove ‘main.py’: File system is read-only)
I also have tried it on another computer and have the same problems.