SL2 Tweeter Advice Sought

I recently noticed a degradation in sound from one speaker and needed (for the first time ever) to move the balance to regain a centralised image. My initial thoughts were that the 250.2 or 282 needed a 10 year recap but the sound continued to worsen over a month until there is now nothing at all from the tweeter in question. 

What puzzles me is that if I push the tweeter dome lightly while playing a track, the sound comes back to a more expected standard. To a non-techie like me this would indicate a poor connection somewhere or is this normal with a "blown" unit?

If the tweeter is indeed dead, are they still replaceable? I will have the pair done but would prefer to take the speakers to a service agent myself rather than go through the dealer/Naim route.

Thanks, Ron