Serious D3s Focus Problem

I have now encountered the same serious focus problem on two (2) successive D3s bodies. The camera intermittently fails to focus at all (no hunting, no lens movement, nothing), or it thinks it is in focus (red eyepiece focus ball lights, camera beeps) when it is grossly out of focus.

1) The problem occurs with both my 24-70 and 70-200VR2 lenses, although it is much more common with the 24-70 (1/3 of the time with the 24-70, about 1 in 15 with the 70-200). These same lenses work just fine on my D300s, D700, and D90.

2) The problem is most frequent if the camera is pointed down, although it can occur in a horizontal attitude.

It can be temporarily eliminated by power cycling the camera, or twisting the focus mount, sometimes. Other times nothing works.

The issue may be with the contacts, although very careful cleaning with DeOxit failed to correct the problem.

Please don't post a lot of helpful replies suggesting I check the focus mode, the custom settings, or something else obvious; these are not the issue. The cameras will focus fine on a specific target, and then stop working completely on the same target two seconds later.

There are very few D3s bodies in use, but I would love to hear of any similar findings. My second body is going back for a full refund tomorrow. I think I will go back to my previous policy of being a late adopter.