Hello,
Thank you for your query.
Could you please tell me what kind of antenna are you currently using on your RUT950 router? In general, since the signal is pretty good it appears that the only thing you could have damaged would be the antenna connector to the PCB. So I would recommend checking it on the router, when ever the thread where antenna is being fixed is solid. It should not move, should be stable.
Signal strength mentioned -77dbm, it falls under the category of -80 dBm to -90 dBm , therefore it is not excellent but it is good. Here is some more information regarding signal strength: https://wiki.teltonika-networks.com/view/Mobile_Signal_Strength_Recommendations
Regarding that your RUT950 has two sim cards unfortunately, it has only one modem, therefore, it can operate one sim at a time. 2nd Sim card can work only as a back up connectivity. In addition, it is normal for your phone to have better internet connectivity most of the time due to different LTE modules used, here is a link to a resource where this is explained in more detail:
LTE speed discrepancies :https://wiki.teltonika-networks.com/view/LTE_Speed_Discrepancies
You have also mentioned that you can receive messages and emails, however, you are unable to view webpages. Did you mean that it never loads at all or just occasionally? If it doesn't load at all, then it could be even a DNS issue, which would result in the router not being able to map hostname to ip addresses: https://wiki.teltonika-networks.com/view/What_is_a_DNS%3F
You could try adding a DNS forwarding of 8.8.8.8 , which is google DNS server.
Here is the link : https://wiki.teltonika-networks.com/view/RUT955_DNS
In addition, I would recommend to carry out an internet speed test, for example ,fast could be used: https://fast.com/
Internet speed test will allow you to see whenever it is really the internet problem or as mentioned, potentially DNS.
You could also download the troubleshoot file and forward it to me so I could have a more in depth look. To download the troubleshoot file please navigate to System -> Administration -> Troubleshoot -> Download Troubleshoot and forward it to me via private message.
Best Regards,
Dziugas