I'd say you are probably close enough in X not to upset things, I would say the left side of the cutter is slightly low hence the pattern in the second photo.
If you look at the first photo the cross hatch only shows where both leading and trailing edges are over the work so there is a bit of ride up going on which the "blunter" inserts will intensify, try it again with a really sharp flycutter and no rounding of it's corner and just a few thou cut.
Also try the same cuts in the Y direction