One of the work D200's messed up in field (specifically why we have two). The AF was only going on hunting trips, it absolutely could not find focus. Manual focus images are not accepted by our software either, so the option of using manual focus was off too. I goofed around with it a bit, swapped out the lens on it, but the problem persisted. I noticed later that at the 18mm wide angle there was some vignetting on the upper corners, I checked the hood and it was on properly. As such, my assumption was that the mirror was offset, so I decided to set to manual focus and release the shutter a few times to maybe try and get the mirror back in place. It worked, the AF is now working again and the vignetting went away, but I am concerned that the problem may persist at later times in field. Is this problem something that requires any repair or tuning to resolve, will it come back? Has anybody else here experience with this problem?