Nikon autofocus oscillation, camera or lens?

All, I would appreciate assistance trying to trouble shoot a problem with a Nikon set up. When shooting with my Nikon gripped D500 my Nikon 200-400 F4 (version I) is oscillating at the plane of focus and will not lock on. This is happening with VR turned off and contrasty well lit subjects and with single focal point or multi point settings. This may be battery related since it seems to be happening at the end of a morning of shooting and the battery indicator on the D500 is starting to show that it is less than full. The camera still meters, releases the shutter at high speed and otherwise functions as it should and there is no battery warning. This problem does not seem to be related to other lenses such as when I switch the D500 to my 300 f4 AFS or my 70-200 f2.8 vr2 and does not occur with other bodies such as my D7200 or D800e. It seems to be D500 and NIKKOR 200-400mm F4 VR specific. I talked with APS, KEH and Photo Tech but no trouble shooting advise could be offered without sending the lens or body in, of course. I have been using an up to date version of the EN-EL15 battery and am surprised at how fast the D500 chews through batteries. Firm ware on the D500 is current. A web search showed a similar problem related to an autofocus contact problem but that does not explain why the problem comes on later in the morning. Your thoughts are appreciated. Thanks

I assume you double-checked that the camera was not switched to continuous focus... apart from that, cleaning the contacts could not hurt since a dirty contact may have a higher resistance, causing a higher voltage drop which in turn may become a problem when the battery voltage drops some. Of course, you could also have some parasitic resistance somewhere in the camera (e.g., battery contacts) or in the lens and it may only manifest itself with the particular lens (or camera) since the electrical properties of different cameras and different lenses may differ.

This may be battery related since it seems to be happening at the end of a morning of shooting and the battery indicator on the D500 is starting to show that it is less than full.

What happens when you swap in a new, fully charged battery at that point?

Does this oscillation occur in all AF modes? In AF-S as well as in AF-C?

Peter I always shoot in AF-C with back button AF-On and the shutter release auto focus turned off. I have cleaned the camera and lens contacts again. Your comment about parasitic resistance may be true. My D500 was purchased as a refurbished camera since I have had good luck in the past with refurbs. Who knows why it was refurbished. I have taken off the MB-D17 grip and will try everything again tomorrow morning. Dieter, I will do a battery swap tomorrow morning when the system starts to act up to see if that is the problem. One additional point is that the problem seems to be only at the 400mm zoom range. Still trying to figure out if its lens or camera or a non harmonious mating of the two. All-in-all this is the first time I have had a problem like this with my Nikon stuff. Thanks guys.

Switch to AF-S and see if that cures it.

 

If the subject or camera isn't moving there's no point using AF-C.

I was able to get my 200-400mm to act up with both D7200 and D500 bodies with fully charged batteries and without vertical grips. As well it fails to lock focus in AF-S. Sent the lens to Photo Tech today.