I have bugged the issue and we are in conversation (the thread is still private I believe), but yesterday I dug (following advice) into the system level via the iDRAC. I posted the following finding that seems significant:
"Attached is the system log from the iDRAC. I note that the error 'System Board OS Watchdog: Watchdog sensor for System Board, hard reset by SMS/OS timer was asserted' is consistent with the reboots we have observed.
What little I can find on this seems to indicate that it is triggered when the system board thinks that the OS has locked up - though this answer was referring to a Windows Update."
We have a response from the team, though we are at (perhaps beyond) the level technical knowledge needed to play at the system level.
In parallel, we have a bug working through the system that the previous boot environment was not available to roll-back. Again, this is bugged and being worked. :-(
I'm impressed with the responsiveness of the ix team and hope that we are closing in on the issue. It's frustrating!
Cheers