Hello,
I have not replicated this, the router successfully connected, after removing a SIM and reinserting a different SIM.
Could you tell, which device firmware version you currently have installed?
Are the SIMs from the same operator?
Why not have both SIMs inserted and perform switch with SMS command switch_sim?
Does pressing Restart connection from router's WebUI Status -> Network -> Mobile page reconnect successfully?
If yes, could you try to configure periodic pings to some remote host for connection health checks and automatically restart connection in case of disconnect? To do this, login to router's WebUI, navigate to Services -> Auto reboot -> Ping/Wget reboot. Create a new or edit existing default instance, enable it, set Action if no echo is received to Restart mobile connection, adjust other settings, if needed, otherwise, leave default values.
See if that helps.
Best regards,
