Failover WAN Link rules

Is there a way to configure which networks to serve a specific network/vlan? I'm getting screamed at by Spectrum because one of my sites has a failover even rather frequently (every other day) and screams through data. Instead of trying to figure out why their service drops so frequently, they want me to set up the cradlepoint LTE modem to be MANUALLY switched in the event of a service outage.

Obviously, there's no way to do this with a vlan and every device being on one switch. If I could define a rule that defaulted WAN access to one VLAN during failover, that would probably make everyone happy.