Volume Knob Cutting out Playback

Ok, so I have an MPC 2000 classic, and just got my phono preamp hooked up to my old turntable, going into record inputs. So my problem is:

When in any mode but sample mode, turning the volume up/down does what its supposed to. When at the sample screen, Mono L and Stereo are perfectly fine volume know works good. But when I swutch to Mono R and turn the main volume knob it cuts out playback of the sample inputs. Like if i put slight pressure on the knob volume comes to normal level, but it is very touchy/picky. Like the knob is contacting something internally to affect output.

I am curious to know if anyone else has had this problem, or what possible issues could be causing this. Like I said, all other modes volume knob has no unusual side effects besides Mono R sampling mode. Any ideas? My volume know is slightly loose (left to right movement), I have yet to open the mpc but will tonight. Is there some sort of base inside the MP for the volume knob I could tighten? Im at work so I cant get into the machine until tonight.

Thanks.

I opened the mpc at lunch and somesort of retaining nut on the volume knob threads was loose, tightened it up and fixed my problem completely. Just got loose over the years. Might be of use to anyone who has a similar problem.

I wonder what it was shorting out or affecting.