USB suddenly disconnecting while Playing

I have a 16Gb stick that i've been using for 1 and half years now filled with Music and never had a lock up since so had forgotten all about this problem, but if I go back to the sitcks I had problems with i'm sure it would lock up again. Delaer also looked and said no fault found.

After several travels to JLR dealer, they finally decided to replace the usb module in the "glovebox" under warranty. Oh miracle! no problem at all since then. All my memory sticks work fine now, no matter they are old or not.
Now I can sing "Happy"