The signal characteristics seem quite good.
Check if the automatically acquired APN is the actual suggested by your provider and, if necessary, set custom value in Network -> Interfaces by editing mobile interface settings and disabling Auto APN.
Currently, your router is connected to LTE band 1. I would like you to navigate to Network -> Mobile, set Band selection to Manual and try the following LTE bands separately: B3, B7, B20, B28.
Otherwise, the device has old modem firmware. Thus, I would suggest to perform an update. Before attempting the update, you need to connect your router an alternative WAN source, either wired or wireless. Below are the the instructions:
- Access your device via SSH and execute the following commands:
- opkg update
- opkg install modem_updater
- opkg install sshfs
- modem_updater -g
- The last command will list available firmware versions. Next modify the following command:
- modem_updater -i <ID> -v <VERSION>
- <ID> - should be 1-1, however, in case of an error you should be shown a correct ID.
- <VERSION> - enter the latest firmware version from the list of the previously executed command, it should be EC25ECGAR06A13M1G.
- So the complete command should look like this:
- modem_updater -i 1-1 -v EC25ECGAR06A13M1G.
See if that helps.