Hi Joe
Sorry for slow response. Regards to filepath - not so far as I know. However...
The first USB stick I used, it turns out, actually presented itself as more than one device. In my case it caused the radio to forget which and where it was up to playing when turned off - starting from the start again.
Maybe it is something similar/same?
From memory the first one I used presented itself as a CD-ROM drive (of small size - used to hold 'helper' software from manufacturer and have it autorun) and then a mass media device (both connected via. a virtual USB hub). The radio would ignore the 'CD' drive and find and play the music on the second drive - but not remember where it was up to (I assume that was a bug or bad program design).