N3 crashed

I have two projects running in parallel each with 3 n3s and 5 cabs.
Most of the processing occurs in the first nodes ie Node 1 for the odd side and Node2 for the even side.
They are close to their processing capacity and a couple of years ago I remember offloading a management tasks from these nodes to their seconds Node 3 and 4 respectively. I can't remember what that configuration item is but I think evidence of it is surfacing in a curious manner:

In my system
Cobranet bundles for cab ids 2001 and 2002 are assigned to Node 2, cobranet bundles for 2002 and 2004 are assigned to Node 4. The other day I walked in and found my project had crashed (Nodes 2, 4 and 6 were muted). Node 4 had a fault indicator on the front and CABs 2001 and 2002 were displaying their ids (not communicating).
When I rebooted node 4 CABs 2001 and 2002 started functioning again and the project became unmuted. (remember the bundles for 2001 and 2002 are assigned to another Nion)

Attached are the messages in the remote log at the time of the crash, sorry if the formatting makes it difficult to read.
I would appreciate any help in trying to figure out what caused this fault. I'm at a loss as to where to start, logs prior to this show no faults and the system has been working fault free for 4 or 5 days since.