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.
It could be an internal wiring issue, or a faulty home hub.
Can you connect things up as shown below, and leave it for a day, and see if you still get the disconnections?
Also make sure that if you do have any extension sockets, that they are wired into that blue connector on the left.