As for the issue of the D7000/D7100...no comparison...look at the difference in size of the sensors...my theory cram a big sensor in a little body with poor engineering (of the foam seal placement maybe?) = problems. Just a theory...
Isn't the FX sensor nearly twice as big as the DX sensors? Add a partnership with Sony to the mix??? Seems like it would be an easy recall and repair but then again...there are all those screws...
Sure, there's a sensor size difference, but think of it this way - the sensor is mounted to a circuit board that sits behind a lens mount that is the same size as that of the DX camera. Sure, the mirror/shutter assembly is also smaller, but outside of the sensor and shutter assembly itself, everything else within the camera should be basically the same. As you can see in the photos below, the D600 and D7000 are essentially the same size, with the D600 standing slightly taller (likely due to the larger mirror/shutter assembly). I suspect the interior fit is no tighter than the DX cousin.
My point is that the flash assembly sits on top of the structure, essentially outside the camera, and any malfunction of that unit should have little to nothing to do with what's going on inside.
If it was purchased new, or refurb, it's a no brainer - return it. If it was bought used, caveat emptor.