Transfer music to USB

Hi all - I do a weekly radio show and generally organise a playlist of music that I own and transfer the playlist to a USB/Flashdrive. In the last week however it won’t allow me to do this - whenever I try and transfer tracks from iTunes/Apple Music I get the rainbow beachball icon - this happens irrespective of whether I am transferring 20 songs or 200. I am, however, able to transfer the music directly from “finder” to the USB with no issues. I’m kind of at a loss and would appreciate any help please!