After a few months of not using my iPod (moded with a 128GB SD card) I charged the battery and it plays normally, but now I'm neither able to add nor delete them. First of all I tried to restore with iTunes but nothing happened and nothing was deleted. And then I tried everything, normal format from Disk Utility, then I tried to unmount and perform this commands:
diskutil unmount force /dev/disk4 diskutil zeroDisk /dev/disk4
diskutil unmount force /dev/disk4 diskutil eraseVolume ExFAT MyName disk4
on this one i get this error:
Error: -69888: Couldn't unmount disk
Also, after formatting on Disk Utility secure option 2 I get this:
posix reports the operation couldn’t be completed. invalid argument.
I already tried to put iPod on disk mode and perform all the same but it doesn't worked.
After all, nothing was erased and iPod still plays songs normally as if nothing happened.
EDIT: When I try to delete some folders manually I get error -50