Navigate to Wan Edge Insights in Mist UI - Application Path Insights. There are frequent events of service path flaps with reason "Unresolved Arp"

The issue can happen if the gateway IP configured on the egress interface is not responding to ARP requests. Run a pcap on the egress port through Mist to diagnose the issue further.

The Application path insights on the same page can also show arp unresolved alerts - this is also related to above scenario. The alert is there for notifying the user that the secondary link might be experiencing some issues and if the traffic does failover to it, the data traffic might get impacted.