When moving from location to location, does the cellular signal of the active SIM-card sometimes completely drop?
Or does the unit keep 3G connectivity?
If the latter is the case, you could try putting the cellular settings on LTE only.
This will simulate a WAN outage when there’s no LTE signal and trigger a failover.
When the MAX BR1 Mini keeps a signal at all times, there is no WAN outage, which means no failover will be triggered.
Another option would be to use multi-operator roaming SIM-cards.
These SIM-cards connect to multiple cellular operators and switch from operator to operator based on signal quality.
The company I work for supplies these, a lot of river cruisers and broadcasters use our SIM-cards.
Our SIM-cards work in 192 countries, on 728 networks.