Thanks, that helps a lot.
In the case of those two images at least, the shift is just one pixel left to right. Looking closely at object edges, IMHO, there is anti-aliasing processing being performed. Depending where the algorithm picks up an edge this could conceivably cause an apparent shift. maybe.
Its hard to tell because even though the compression is set very low, at the pixel level the compression artifacts make it difficult to know what is the scene changing vs random noise.
Do you have a adjustment for sharpness? Another wild guess, but maybe the anti-aliasing can be indirectly controlled by setting this lower.
Is the compression set as low as it can, and/or is their any other image processing going on that you can temporarily disable?