kolladmin,
A few things I would try on the RV220W:
1) On the IKE policy, change the exchange mode to Aggressive
2) Make sure that Dead Peer Detection is enabled
3) On VPN policy, disable PFS Key Group
If the settings are already configured, try the opposite settings and different combinations. My guess is that there is an issue with the LTE connection so this can be hard to troubleshoot and make work consistently. Don't be afraid to experiment.
- Marty