Yes, that's correct. You need two drives on the device. XD2031 will do this properly and Andre' recently fixed some problems with REL handling that had prevented OS-9 from working. I'm currently...
If that does not help, there are separate pins from the drivers that go to the connector so it is possible that there is a bad transceiver signal at the connector. Repeat data bus test with 55/AA hex...
Save yourself some time without all the fuss and...
Save yourself some time without all the fuss and just grab an old mobo and an old HD or floppy and go from there.
Agent Orange Today, 11:03 AM