Back to your provider to have them fix this one.
I have a Huawei e5186 LTE CAT6 Router with an 150/50mbits connection. I recently came across this very weird bug, where from inside the network certain websites (most of the time ssl servers, but not all of them) just will not load. The browser attempts to load but eventually just gives a timeout error. Sometimes when i reload the websites they suddenly work, sometimes they dont.The websites itself are also not persistent so one website might work and 5 minutes later it just wont load or very slowly. The error occurs from every device inside the network. The interesting part is: when i acess a device from outside the network using for example teamviewer the connection works fine. But if i try acessing websites on the remotely controlled device it gives the same timeout error. So it can't really be the connection, as the connection itself obviously works. If i try to ping websites, sometimes it works, sometimes there is packet loss, however, dns resolution always works.
I am very thankfull for any ideas.