Nikon USA returned my D600 to me after I sent it in for warranty repair for addressing the oil splatter marks on the sensor; according to the note the shutter mechanism was replaced (B2- shutter mechanism replaced). I verified the sensor was totally clean when I got it back. Now, 500 shots or so on, without a single lens change & shooting exclusively with the 50/1.4 indoors (and the lens has a dust gasket), the oil splatter is all back! There are dozens of oil spots (not dust bunnies) on the top left (I reckon the majority, about 60% of them) and top right (the rest 40% or so). DOZENS. That's a third failed "moment of truth" in my book in regard to this camera. First, the camera has a problem they do not acknowledge; second, they promised to send me a shipping label but did not until I escalated the issue, and third the 'repaired' camera comes back with a creaky seam and a sensor that still develops the (unacknowledged) oil splatters. To say I am disappointed is understating it. Question: has anyone faced this issue? According to my web research, the spots are all supposed to go away when Nikon USA replaces the shutter mechanism on the D600. So what could be happening?