UPDATE:
After trying half a dozen USB hard drives that have worked successfully in this DL32R with MF4x, on a whim, i put a USB thumb drive in and it saw it!
But it was unknown, so I formatted it.... Then I recorded to it with the DL32R and each recording showed on the list when it completed.
BUT - plugging this thumb drive into Windows based computers resulted in the device being recognized as a USB drive, but does not show as a disk with a drive letter.
Information states it is a removable disk of 32GB capacity, Partition style MBR and it's "online" with a healthy, active and primary partition)
I cannot change the drive letter - nor can I format it in a windows machine from within Disk Management, but deleting the volume will allow it to show up in file explorer, but I cannot format it from there, says "unknown capacity".
Putting it back in the DLR32R, it again says it is unknown and let's me format and write to it.