If there are two wires free that originate in the incoming cable then probably nothing to worry about.
As for improved results after removing face plate with nothing attached, the chances are that it is a bad connection from test socket to face plate or face plate to filter. Check that all four sprung loaded contacts are down enough that they will bend when the plug is inserted. Then insert and remove the face plate several times and then the same with the filter into the face plate - it will remove and grime or corrosion.
Just for completeness can you host an image somewhere and post a link?
M H C
taurus excreta cerebrum vincit