I am (still) using SW Premium 2016, 64-bit SP1.0 on a quad-core platform running Win7 Pro (100% up-to-date w.r.t Windows Updates) and  with AMD FirePro V3900 graphics card (& video driver's up-to-date).

I was trying to create a Circular Pattern from a Swept Boss feature.

The swept boss consists of a circular  profile swept along (in my first attempt) a rectangular sketch with sketch-radii corners. This failed to create a circular pattern, even though the Preview looked very promising.

After looking into the Forum, I found a posting wherein somebody had a similar problem; they used the Fit Spline function (Tools>> Spline Tools >> Fit Spline) to create a (continuous? seamless?) spline that followed their original sketch geometry. They claimed that this technique solved their problem, after they had sufficiently reduced the spline step (increment) size.

So my second attempt was to create the Swept Boss using my original rectangle-with-sketch-radii-corners sketch, fitted with a spline with the Delete [original] Geometry option [that is, such that the Boss profile would be forced to follow the spline, not the original geometry].

Using the Fit Spline function to generate the swept boss's sweep-curve did not result in the circular pattern, even after fiddling with the Spline step-size down to 0.000001 (far smaller than the default. Note also that I had deleted all the previous steps and re-saved the model prior to attempting a rebuild of the Sweep and re-attempting the Circular Pattern, so that there was no possibility of some lingering file in the background disrupting the outcome).

The odd thing is, that during the Circular Pattern properties dialog, one can see the Preview of the circular feature...but it never materializes a permanent Circular Pattern when you select the green check-mark.

See photo, here, of the Circular Patterns property-dialog Preview:

Any idea of what's gone wrong?