Believe me, I've purchased several vintage drives off eBay over the years that arrived DOA.

It's no longer cost effective to pay $50 for a vintage SCSI hard drive on eBay for it to either arrive DOA, or die shortly after installing it. Now, they're regularly posted for anything between $30 and $50 sometimes higher. Finding an old hard drive on eBay for $5 bucks used to be commonplace. I've really been wanting to get away from old spinning platter based drives for a while now.

Then again, I don't know if that drive is having issues of its own, or if the internal drive is wreaking havoc on the SCSI bus. It's more reliable than the internal drive, but it too sometimes doesn't appear in the Finder at startup. Unfortunately, that drive is starting to flake out too. Luckily, I have an external drive that I copy of all my apps, files, and disk images to for redundancy. It's only a matter of time before the drive completely dies. It's been like that for about 2-3 months now, and it seems to be getting worse. Sometimes I can launch an app and run it without issue, but then the whole machine hangs when I exit the app.

Sometimes it hangs at the 'Welcome to Macintosh' screen. Sometimes the SE boots all the way to the Finder without a problem. Sometimes the drive is detected, sometimes it's not. The hard drive in my Mac SE is on the way out.

Mac system 6 emulator