What I would recommend that you do, is to fit a filtered faceplate which replaces the bottom section. It very easy to fit, and your extension wiring connects to the back of it, and is filtered to prevent the broadband signal getting into the extension wiring.
You will no longer need to use any microfilters.
The one shown below, is compatible with ADSL and VDSL (should you upgrade to superfast fibre at any time) If you look on Amazon, or other online sites, you should find it,
Meanwhile, you might like to try removing the wire from terminal 3 at both ends, as this is the bell wire and is not used anymore, and causes line imbalance, which can cause disconnects.
Remember to leave a microfilter plugged into the extension socket, until you have replaced the faceplate with a filtered on.
You may also find an increase in connection speed, when you fit a filtered faceplate.
