"Is there something about the D200 sensor that causes this ?" Well, my D200 does not exhibit this behavior in the studio (or anywhere) - nor any other D200 that I have heard about. So I don't think this is a common issue.
Since you state that this only happens in the studio it is highly unlikely it is a camera sensor issue. If the sensor had a problem it would show up in other situations too, not only when shooting in the studio. What do you do differently when shooting in the studio than when shooting outside? Since the issue shows up when you shoot in the studio, it is much more likely that the issue is something that is done differently (or set differently) than when shooting in other locations.
For some additional troubleshooting, maybe you could start by setting up the camera for some outdoor shots, shooting a few image outside and then take the camera into the studio. At first, shoot without making any changes to the camera settings, and then *one by one* introduce any changes or settings that you normally use in the studio. Making careful notes about each change would probably be very helpful, rather than trying to rely on memory for your after-the-fact analysis of the images.