Hello,
Indeed, that sounds weird. Could you try updating one of the modems by following the process described here and check if the issue is still present?
Nothing is blocked from the router itself, so I suspect it may be a network issue. Try setting the MTU to 1350 by navigating to Network → Interfaces → General, edit mob1s1a1, and in the Advanced settings tab, set the Override MTU option to 1350.
Let me know if that helps!
Best regards,
Best regards,