From previous posts it appears the Mac has a strange ways of doing things. I don’t use a Mac. Then of course there is always the MSC/MTP issue. I can tell you what will work, save everything to your computer using whatever mode shows your files, try both modes. Switch to MSC, format the device via settings although formatting under windows is fine. Then use windows to move files back to the device and never allow the player to switch out of MSC mode unless you use protected music…
If you use DRM music, you will be forced to use MTP mode, in which case you will need to use only that mode.
Switching modes or platforms can cause problems if you ignore the issues involved. Deleting files doesn’t save space if the system uses some form of trash recovery. This doesn’t seem to be a problem with windows and removable devices.
