Right side speaker cutting out periodicially, no obvious cause

My Index's right speaker is frequently cutting out during use, especially if I pull the headset off my face to adjust it or apply any pressure to the bottom right of the headset, which is making me think its something internal that's causing it. So far I've tried these solutions:

• cleaning the contacts with alcohol
• replacing the speaker entirely
• using a different trident cable
• putting an o-ring around the mounting point

I've had no success. I can't find any breakdowns of the mobo that might detail where the speakers connect up to it, so I'm nervous to go rooting around there without knowing what I'm looking for. The unit was bought refurbished over a year ago, so I don't have a warranty to claim unfortunately.

Any ideas?