VoIP and Multi-WAN Failover

[The Hammer]

I am running one ATT and one Comcast line currently, and have failover setup correctly such that my tracert'ing shows correct paths when testing the failover. HOWEVER, all of our RingCentral phones will NOT work again until the phones are restarted when the ATT_NFE0 interface goes down..

I'm starting to pull my hair out, and aside from editing the apinger conf files manually to reduce the time it takes to notice a downed WAN to .5 seconds on these steady connections I have no clues as far as what else to try to attempt to make this failover work for our network.

We have a CradlePoint router that doesn't seem to have this problem when failover takes place, what gives?  ???

Anybody have any ideas? I'm using pretty basic static DHCP for the phones, automatic NAT rules, and the config info that I believe is all the relevant info is attached.. Thank you all for your help in advance!