SendTo 65 & MultiWan Failover

[Ximulate]

At a remote location, we've had multiwan failover working well for awhile now. Today, a remote location had a short power outage. The power came back on, but the internet did not nor did it failover. About 12 hours later, the primary WAN came back on and I was able to remote in to view the logs filled with SentTo 65 errors. This post explains which it magically started working 12 hours later.

In this condition, what do I need to do to get it to failover? Would chaning the Monitor IP to a server outside the ISP network work (i.e. 1.1.1.1)? There seems to be some debate about the merits of using an outside server for monitoring.