I have a CS-MKIII, never had a problem with the SCSI, so other than standard SCSI voo-doo troubleshooting, I cannot offer much help. I'm using an IBM 18GB LVD/SE hard drive, had a Plextor wide-SCSI CD, and a 50-pin Zip drive with a Datamate 68-pin to narrow adapter. The Zip drive is gone, now, and the Plextor wide has been replaced with an Acard SCSI-to-IDE adaper on a DVD drive.
The entire bus is terminated. Never had a problem.