For the Xtreme 1.3 firmware, if you are upgrading from 1.2, then all that has to finish is 1, 4, 8. All the rest can fail IF UPGRADING from 1.2. If you are starting fresh, it has to be 9/9. Also, it is ALOT easier when working in safe mode, the drives flash faster and more stable in it.
Recap> Upgrade from 1.2, then 1, 4, 8 must be good, rest can fail.
Fresh flash, all 9 out of 9 must be complete.
PS. Gary is working on the flashsec command. Most of the time it reports not flashing when in fact, it did, with success. Just be patient people