MDI problem

I've got a problem with my MDI and I'm wondering if anybody has experienced it.

Sound quality varies and it'll only send sound to the kerbside speakers. If I wiggle it all about in the armrest I can get it to come back to both sides for a while. I've replaced the cable to no avail and tried a different USB stick so I think there must be some dodgy connections, presumably at the arm rest end.

Has any body had this problem? Has anybody solved it? I'm fairly competent with most technical things though I've always regarded electronics as witchcraft... but I'm willing to have a go at sorting it out if I have a rough idea of what to do. Failing that, as a last resort I will disconnect the MDI in the armrest and install a new one in the glove box but I would really like to fix the one that's already there.

Any thoughts?