Default Route Goes inactive on bonded interface

I am running a pair of CCR routers with 6.20 in them one is a CCR1216-12G and the other is CCR1036-8G-2S+ where
we are adding our new 10 gig fiber. I created a bonded interface with 2 slaves to carry the data to our NAT firewall.
The NAT firewall has a default route across the bonded interface to the edge, when I move traffic to it, the route goes blue and
unreachable after a few minutes and traffic stops flowing. I can still ping across the interface.

As soon as I disable and re-enable the route it comes back to life for a while before going inactive again.
Obviously I cant put this into production.

Is this a known issue? Has amyone else encountered it?