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Normal tolerances would not be resovable by the sensor. You have an issue. The problem with observing so many bad copies (with poor tolerances or whatever) is that the maths quickly stacks up against you.
Say 1 in 10 Distagons is a dud (Which is very high). To get 4 is like 1 in 10 to the power 4, = 1 in 10000!
We can exclude bad batches as the lenses are across 2 manufacturers. Buyers of these lenses are experienced and demanding of their equipment, and if this was prevalent then it would be widely acknowledged by now.
Rather than claim Oly's are great and there is an issue with Zeiss / Canon QC as factually as you did, you need to study your equipment / technique to work out what is going wrong.
Mr Joe wrote:
Again, it's not a bad lens or a bad camera, it's the combination of a lens tolerance that's off one way, with a camera that's off the other way. Both can be within spec, and you still don't have a sharp picture. And my testing showed lenses that were off on the left side, and others that were off on the right side -- with the same body. Yet all of my Oly lenses worked fine with either body.