Twenty minutes is way too long. Also, the blink pattern doesn't look like the surface scan to me --- that's more of a steady, rapid flashing, at least with a healthier Widget.
Naturally my first tool for investigation would be
NeoWidEx, although two things:
1. my guess is that the drive is not getting far enough through the boot process to want to talk to the Lisa yet, so NeoWidEx won't work
2. NeoWidEx is not an automated diagnostic tool: you really do need to read the "required reading" and then put on your detective/diagnostician hat
One thing the blinking reminds me of is times when I've turned on a Widget after years of idle storage. The lubrication around the drive head arm gets sticky, and when the Widget tries to swing it, it can't articulate it all the way. I've run into this a couple times, and each time I could tell by listening carefully that whenever the Widget would power on, the head actuator would be able to swing the arm a little further. Presumably the lubrication was warming up and gradually getting looser.
So, without more intensive diagnostic tools like
UsbWidEx (which is really the most powerful Widget debugger I know about, since it can investigate some issues without the Widget being ready to talk to the Apple), you might try the following. Attach the Widget to the Lisa, boot into BLU, and send it reset pulses every few minutes for a little while. See if you can notice subtle changes in what the Widget does each time --- how long it takes to blink, or whether the arm actuation sounds any different. If things seem to be progressing, keep doing it; with luck the arm will eventually recover full travel.
Note that this suggestion may put data on your disk at risk --- if the Widget decides it
can move the arm, but then for some reason it can't or it's still sluggish, it may behave in a way that the authors of its firmware failed to anticipate or control for. You might want to devise a different method if the data on the Widget is too important to lose.
(Finally --- even though I've seen a few Widget problems in my time, I haven't seen them all. I don't know how a Widget misbehaves if the optical track gauge breaks, for example, and since that also concerns the arm, maybe it can cause a similar behaviour.)
Good luck!