RN31400 6.10.6 Locks up or out of memory errors. (BTRFS)

Hi All, 

Having done some searching of the forum and the internet at large, I'm struggling to sort this NAS box out. 

The issue :-

The box boots normally but after around 20 minutes, it either locks up with no error, responding to ping but nothing else; or it gives an out of memory error. 

In either case, a reboot will bring it back to life. 

What I've checked/found. 

Getting connected to the CLI, top shows the BTRFS-Transaction service hitting close to 100% CPU all the time. Ram use climbs slowly, until either of the two above happen. 

I've disabled as many services as I can in GUI, so it's just got SSH, HTTP and HTTPS available.

I've attempted an OS-reinstall, but there is no change to the behaviour. I can't do a full wipe, as the data is required, and is not backed up elsewhere. 

Attempted to disable quotas. Doing this through the GUI seems to work, but the box still crashes, and when it's rebooted, it comes back with quota on again. doing it through the CLI doesn't seem to have an effect. The command is accepted, the CLI drops to the next line, with no prompt and it just sits there till the box dies again. 

To try and alleiviate the issue, I've swapped the RAM out from 2GB to 4GB. This increased the time between crashes slightly.

I've not found anything else relevent to try, so I'm looking for more suggestions...

Failing that, is anyone aware of any software/tool I can use to recover the data from the Raid Array, if I move the disks to an alternative machine.

Many thanks, 

Steve D.