This probably won't help, however, i'll offer it in case it does.
I updated to 11.3-U2.1 today and I had quite a few problems but it worked out.
1. I activated the update from 11.3-U2 from the Web UI. via "Check For Updates"
2. It started downloading and got to 65.2% and froze for over two hours.
3. When I selected "Check for Updates", FreeNAS told me the update was complete, however, there was an animated icon (next to the Task Manager, power etc. icons, top right). It suggested I reboot
4. I rebooted the NAS and after 30 minutes, it had been frozen at one particular line (can't remember which message)
5. I rebooted the NAS again and after 1 hour, it finally booted into the GUI. There were a number of messages indicating it was "updating" still.
This probably won't help you. However, whenever I reboot, it's always a "controlled shutdown".
Good luck. I hope someone else can help you.
FYI - I think my old NAS may have been corrupted by the "critical bug" that's been fixed. I've spent a week trying to recover that NAS. I really appreciate the free tools provided. There are many volunteers who have put a lot of time into improving what we have today. It's not perfect, but, it's excellent considering what is provided from people's generosity!
