Assembly constraints do not work correctly for all parts

Problem

In an assembly, you can set, for example, a coincidence constraint between parts, but the parts move incorrectly relative to each other, meaning the constraint does not seem to work.
It can also happen that, for example, a concentricity constraint cannot be applied to a cylindrical surface, or a component handle cannot locate the center of a circle.

Solution

Very often, the "problem" occurs with parts imported from another system (e.g., in STEP format) whose surfaces are spline-based, even though they appear as planes or cylinders. This can cause positioning to behave incorrectly.

The part can be easily fixed: in part editing mode, right-click → ACIS Geometry → Heal → select Simplify…. This function converts spline surfaces into planes, cylinders, or cones according to their shape.

You can check a surface type in part editing mode by hovering the cursor over the surface:

Using the part healing Simplify function will "fix" the surfaces:

You can verify the result afterwards:

After this, part positioning will work correctly.

Try first with the default tolerance. If that does not help, use simplification with a specified tolerance and increase the tolerance value.