Actually come to think of it, I don't think that's it. A couple of times, when it hasn't worked, after I pressed the eject button and took the faceplate off, the motorised bit it clips to didn't go back up. Sounds like something else?
Umm, because I have a P860MP also. You can also order that part on pioneers website. I would call Pioneer myself or email them because the 860MP has problems with the motorized face, and who knows more about it? PIONEER! yep. Try them. You tell them the problem and since they had a lot of problems with this model they should know what the problem is and tell you what you need to fix it.