There is an issue with one of your disks because it has a duplicate UUID. You can fix this in UD settings by creating a new UUID.
May 30 22:31:45 Tower unassigned.devices: Adding disk '/dev/sdy1'...
May 30 22:31:45 Tower unassigned.devices: Mount drive command: /sbin/mount -t xfs -o rw,noatime,nodiratime '/dev/sdy1' '/mnt/disks/WDC_WD80EMAZ-00WJTA0_1SJL8HJZ'
May 30 22:31:55 Tower kernel: XFS (sdy1): Filesystem has duplicate UUID e406c996-a5c7-450c-bde9-bc2f889ce9df - can't mount
May 30 22:31:55 Tower emhttpd: read SMART /dev/sdy
May 30 22:31:56 Tower unassigned.devices: Mount of '/dev/sdy1' failed: 'mount: /mnt/disks/WDC_WD80EMAZ-00WJTA0_1SJL8HJZ: wrong fs type, bad option, bad superblock on /dev/sdy1, missing codepage or helper program, or other error. '
Your thumb drives don't show any indication of errors. It's almost as if they mounted, but UD doesn't pick that up. Post the output from the following command:
mount