Well, I had a program that could examine the home blocks, and I knew where to find the backup home blocks. So, I hacked that program to copy the backup block to the main one, and then change the checksums to agree.
That is one way to avoid a very long restore :-)
The other issue is the voice coil could suck dirty air in during long seeks, so they had ti replace the HDA and put a filter over the air exhaust from the voice coil.
Yes, they had issues. Another one apparently is the heads will glue themselves to the drive after a few years, I was researching ways to unstick the heads without damaging them (hint: Never use Isopropyl to clean a RM03 disk head. It will unglue it and hilarity will result) but that whole thing was mooted when it vanished.
MASSBUS was not anything like a UNIBUS, it was a lot closer to an IBM channel bus and tag cable.
Ok, however the address and data bus feels a lot like a Unibus. And all of the registers are in the drive controller/adapters, it almost feels like you are tickling the adapter directly off the Unibus. Given Dec's joy with Unibus repeaters, bridges and windows it does feel like a window into the Unibus itself.
C
