Welcome to this user forum.
Is there any noise on your phone calls? Dial 17070 and select option 2, there should be no noise between the announcements.
So you have the home hub plugged into the top one, as it should be?
The master socket could be faulty. Do you have a microfilter available, if so, can you remove the bottom part of that master socket, and plug a microfilter int the test socket, and the home hub into the microfilter?