Milling round pocket ends with flat bottom

[paulericFEV2X]

I have 15.875 radius open pocket I need to mill, and after doing a 3D Pocket clearance with a 1/4" bit and a 3D Countour with a 1/2" Ball nose bit, I end up with a flat bottom.

I tried about 50 permutations of settings and can't get it right.

Here are my last settings for the 3D Pocket Clearing

And my settings for my 3D Contour

Any idea how to get rid of it?