Sandisk ultra fit 32g 3.0 unable to copy files, why?

[AC Question]

I have been using a 32g Sandisk Ultrafit 3.0 and OTG with my Samsung Note 4 for sometime now and I've never had a problem since yesterday, when I decided to clear all files and just load music so I can just leave it in the car.. I have all my music in my Note 4 so I got the OTG cable and plugged the ultrafit, then I started marking the music i like and pressed copy. A few seconds into the transfer, it would stop and show a message saying 'file transfer failed'. I have tried reformatting the Usb but to no avail...I don't know what to do, please help.