The 1st is the AKAI in that case.
I have no idea what happens in your system,- I never thought of terminating IB103 and I think it´s by default anyway.
In my system, I connected to Synthax/Hybrid Arts Syndrives ( CD-ROM & HD) to IB-103 and the MOD is the last in the chain after the Syndrive,- MOD active terminated.
Works w/o issues.
Maybe you have a SCSI ID conflict.
Switches on HD enclosures showing a ID number doesn´t mean it´s the right one,- that´s why I check SCSI drives w/ Mac and SCSI director.
It all depends on the pinout of the SCSI ID connector of the HD and that at the cable of the enclosure.
You can measure the pins at the HD and the pins at the plugs of the SCSI ID cables w/ a ohm-meter to find out what´s ground and what the other pins are.
If someting isn´t connected correctly, SCSI ID #1 showed at the enclosure´s ID switch results in ID#4 in real or #3 is #6 then and so on.
I have a question about term ON / OFF on IB103 internal SCSI , It must be terminated on external connection when I plug in a drive?