Rotating part and measurement doesn't follow

[[Cl...]]

Hello all,

I have a part with a center bore and 8 more smaller cylinders around the center bore. Attached is a very rough drawing of the part.

My alignment is a plane at the top of the center bore, the center bore itself as a cylinder, then the top cylinder as a circle for rotation.

The measurement that's giving me trouble is the parallelism of the top bore to the center bore. I have 2 circles that are recalled into a 3D line in the top bore (The base alignment circle is not one of them) and 2 circles in the center bore also recalled into a 3D line (once again the base alignment cylinder isn't included).

When I run the part, the top bore fails. When I rotate the part 180 degrees I would expect the failure to be on the bottom bore but it is still the top bore. This may be a "duh" moment but I haven't came across this before and it has me stumped. Any feedback would be appreciated.

Rough drawing.PNG

[[Ju...]]

Does checking them as cylinders instead of circles for the parallelism characteristic help? That way, they each have a measured axis instead of a recalled one.

[[Ow...]]

Food for thought.
Possibilities:
How deep are the cylinders or the depth of the farthest recalled circle ?
Depending on how deep the cylinders are and your probe to shaft radius difference, you could be shanking out on the probe shaft on the bottom circle if the part isn't fixtured square enough to the Axis/probe and cause the line to not be truly in the center?
Are the bottom circles of each cylinder measured at the exact same depth? Just a bit different of depth might be why the bad top doesn't check bad when rotated 180, if that feature depth is different.
Have you looked at the form/roundness and size of each circle measured and see if there is any big difference between the top and bottom?
If measuring as a cylinder, use a minimum of 3 equally spaced circles in the cylinder strategy.