Sometimes depending on how the files were copied to the device, it stops to play, randomly on a part of the memory.
On linux/debian I tried to use carefully:
"lsblk" or "sudo fdisk -l"
sudo fsck /dev/sdb (or with switch -a)
which seemed to work.
How it could be done for example with a chkdsk thru commandline or gui on windows, if the device is not recognized as a drive ?