- The telco is free to roam subscribers.
- Subscribers not producing traffic might be disconnected after a while from the WAN and have to re-establish the connectivity.
- When LTE is not available anymore - or signal is too weak - OWL-LTE can change to 3G, but this will cause an interrupt because it's a change of technology on provider side. When the signal is strong enough OWL can move back to LTE. If this situation occurs often, it might be useful to force OWL to use 3G only to avoid frequent interrupts or - if possible - to use a more powerful antenna.
I recognize frequent mobile network (WAN) link interrupts. Why? - ナレッジベース / Products / OWL - Belden Support Center
There is no guarrantee for availability.