RN1044 6.5.2 can't login

Ok - I have an RN10400 thats been running well for years. I have four disks with a fair amount of data in Raid Pairs.

We had it on network 2 (192.168.0.X) working with Active Directory linked to a Server 2016 domain.

There was a VPN link between that subnet and network 1 (192.168.20.X) that had another two servers in the same AD domain.

The two branches moved into the same building at the start of this week and the network 2 2016 Server had its IP changed to the 192.168.20.X subnet and all is working well. EXCEPT for the ReadyNAS.

It still has a static IP bound of 192.168.0.251 to the top NIC and the lower NIC is on DHCP. It doesn't seem to matter what I try but I can't access the data (Even though RaidAR and the LCD all reports thats ok thank goodness) or the Admin page. With the admin page I get there from time to time and the initial page loads but rapidly anything I click on I get the spinning wheel and then "Connecting to the ReadyNAS Admin Page".

Maybe its because its stuck retrying trying to talk to the A/D server to download a list of users?? I can't tell when address I had in there - Perhaps I had a full DNS name for the server - Maybe I had an IP. Its a busy network so trying to put the server and router back to their old IP's is probematic to say the least and to be honest I'm not 100% sure what IP it was previously on.

Sometimes when I first get to the Admin page it offers me a firmware update to 6.10.X (Can't remember last digit right this second) but I'm nervous to push go incase it fails to update and makes matters worse.

Perhaps I need to download the firmware onto a USB and do an update - If thats the best way to proceed can someone point me to the process and assure me that the drives will remain accessible after the update (assure to the normal but you really should backup first level). 

They have backups of a good chunk but due to a lot of data movement and archival lately its not all backed up.

I've seen a fair ammount of talk like this for 6.5.2 so not sure if its a bug or if its because its stuck trying to sync the user list from AD (But then I guess thats a bug that it renders the NAS unusable)

I managed to download the logs last night to my laptop at home when I experimented with setting up the right subnet on a spare router that gave internet access. Today I can't but RAIDar doesn't run on this pc - It runs, starts the search and closes so I'll try on another PC. Will the logs indicate the name/IP of the A/D server its looking for - I could find reference to it looking and the AD domain name but nothing referencing how it was trying to contact it.

Please Help - Terrible time of year for it.