My Router Huawei Echolife HG8247T Is Not Allowing Multiple Connections to the Server

Hi there.

I just shifted from a DSL connection to a GPON connection and the new router Huawei Echolife HG8247T has a very peculiar problem.

For example, I started an HTTP server on port 80. The online port checker utility showed the port as open. I can also open the index page on my phone with a hotspot(accessing outside the network). But when I interrupt a loading page. I am unable to access the server again. Suddenly the port also closes but can access the server locally in a normal way. The port is only open after a few minutes.

The same goes with windows remote desktop, welcome screen for the remote pc appears, i closes the window or connection and the port closes, and am unable to connect to the remote pc for a few minutes.
The same goes with Teamspeak servers and call of duty dedicated servers.
I have been hosting HTTP and ts servers for more than a year and I have never had any kind of this problem on the previous DSL connection.
I have even tried turning off Battery Saving and DOS firewall.

Thanks.