5d3 and 100-400 L - slightly loose mating to body?

When I have the 100-400 on my 5D3 body there a very slight "play" in rotation, about 1/2 mm.  I.e., with the lens mounted I can rotate it back and forth ever so slightly.  It doesn't seem to affect sharpness, which is excellent.

Is this something I should be worried about?

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Jim Garrison
jhg@acm.org