Partial downloads. songs come into player and can be played through usb cable on computer in its

Question

songs come into player and can be played through usb cable on computer in its entirety, on the player I get a few seconds and it goes to the next song. I have deleted all of them. One folder cannot be deleted...........it is empty but won't delete............don't know if that is part of the problem or not. I'm wondering if the whole player needs to be reformatted and how to do that.