I checked the blog for router failures:
25th May WAN1 fail 22.48
26th May WAN1 fail 12.oo
27th May WAN1 fail 20.20
2nd June unspecified 14.00
8th June WAN1 13.50
9th June WAN1 22.45
I had thought the failures were on both routers - this indicates it could be a problem with hardware of just one router. I called Be they requested I update the firmware before they replace the hardware.