This is very confusing. I have noticed some other inconsistencies. When I specify a clipping panel I have to give exaggerated values for the clipping size x and y to make it behave correctly in game mode - but it looks wrong in the inspector view.
I don't know if this is related at all to the dragging problem, but it appears to be "off" by about the same scale (around 1.75).
I have checked EVERYTHING in the tree to make sure the scales are all set to <1, 1, 1>. The only exception is the UIRoot. It has a very small scale <0.001953, 0.001953, 0.001953>, but I suspect that's normal.
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P.S. I am willing to send you my scene, if it comes to that.