The distribution cables that supply your broadband were installed for telephony, not the sort of frequencies in use for broadband today.
Do you check stats regularly? If so has the hub been dropping connection? Often?
An unstable connection can result in a drop in connection speed. actual connection speed is normally Closer to attainable than yours currently is showing
I probably was one of the first in the cabinet, however, if crosstalk affects the integrity of the signal to the extent that it appears to be doing (2013 to now) about 17Mb/sec then there is a problem with the cabinets in general (I am an ex-forces electronics engineer).
I would expect that all cabling should be screened to prevent such a degradation (21%).
Take a look at here for information on crosstalk :-
An RCD will trip if there is an imbalance between the current flowing out on the live, and returning on the neutral. So a breakdown of insulation, a worn out switch, or a loose connection will cause this. Perhaps something has been spilled on the switch, see if its only element of the cooker.
I would get the cooker checked by a qualified electrician with the correct test equipment, rather than suspect the RCD.
As this is off-topic, it may be best asking on a more specialised forum.