GL-MT2500A brume 2 no cable detected

I just purchased a new brume2 and after first setup I detected that the router looses the network connection every 10-20 sec.
Tried different network cables and checked network connection. In my local lan are about 20 devices with perfect working internet connection, so the issue is with the router.
I updated the firmware to the latest 4.4.6 version, but this also made no difference.

Is this the case before the update to version 4.4.6?

Before and after upgrade… The upgrade didn´t change the behavior…
I also changed to fixed IP settings → also no difference :frowning:

It seems that a problem with a router before the brume caused the trouble. No it works fine