Troubleshooting fundamentals: Lowest Common Denominator (LCD), meaning 1 drive, 1 simple cable, 1 basic SCSI host adaptor, and preferably an external terminator.
The few "Auto-Spin" (a.k.a. -- "Auto-Start") jumper problems I've encountered in the past were all where the drive would NOT spin up at all until the Auto-Spin jumper was removed from the drive, followed with setting the SCSI host bus adaptor BIOS to "Send Start Command" to that SCSI target ID. In other words, hardware Auto-Spin quit working altogether, but a SCSI command fro the SCSI host bus adaptor over the SCSI bus would work!
In working with several hundred SCSI hard drives over the years (since mid 1980s, in fact) some other SCSI strangeness that I've ran into was an early IBM drive that suddenly one day became SCSI ID "3" no matter what I did to its jumpers. Neither of the two different sets of ID pins on the drive were physically shorted, but obviously a short existed somewhere -- in this case, somewhere in the hard drive's SCSI controller circuitry. The drive, otherwise, worked perfectly for many years -- but *only* as SCSI ID "3." I recall someone else telling me a while back about a SCSI drive that was stuck at SCSI ID "0" no matter what they did with the ID jumpers.
A more common problem that I've ran into on older SE (non-LVD) SCSI drives was poor or bad onboard drive termination. On long and/or multi-drive SE SCSI busses it's generally well advised that you go with an external terminator.
Not so much of a drive problem, but a problem that can really get one rather angry once you discover it, is BAD JUMPERS; they can look perfectly good, but they're most definitely bad. I've ran into bad jumpers maybe a dozen times. So, I'm always pretty cognizant of the possibility of bad jumpers when I encounter "SCSI Strangeness."
Just thinking about SCSI problems always makes me recall the time -- in 1991 or 1992 -- where I had a external Toshiba 30 MB SCSI drive with fairly important data on it to die on me (would not start up). I worked and worked with it for a couple of hours to no avail. I had pretty much discerned that the motor was locked up or had become weak, or possibly that the heads had stuck to the platters, because I could barely hear it trying to spin each time I applied power but was being held back. The drive always ran cool in its external case, so I never really believed that the heads were stuck to the platters (from excessive heat).
Finally, after a couple of days of occasionally tinkering with this Toshiba SCSI hard drive and getting nowhere, I decided that I would need to take some drastic manoeuvres to "free up the motor" by hitting the top of the drive mechanism with a medium-light-weight ball peen hammer with the drive laying flat on a carpeted concrete floor. At the same time I powered it on, I would give it one dead hit squarely in the middle of the top of the drive on-axis with the spindle. I did this 7 or 8 times increasing slightly the strength of each dead blow. There was still no change. Then, I decided to just deliver a single serious hard blow in the same spot on the spindle bearing. WHAM! Nothing. I figured that the drive would've probably cracked open from such a hard (and loud) hit. Then I hit it 3 times in swift succession just as hard as I did before. Still nothing.
I stared at the drive for about 10 seconds -- thinking. I walked over to my drawer and put on a thick canvas+leather construction glove to protect my right hand just in case the wooden handle should break, turned the power on, and immediately swung the ball peen hammer with a high-speed savage hit -- complete with my feet coming off the ground. Suddenly, the drive *slowly* began to spin! I just let it sit there and run for about an hour before turning it off and hooking it back up to the Macintosh's SCSI chain.
I thought that the casing would have shattered from such a hit, but it didn't. The ball peen hammer wasn't very heavy and the handle of just average length, so that save the drive. Incredibly, that stupid Toshiba SCSI drive was used for about 4 more years (non-valuable data).