The following is taken from the original announcement on TwistyPuzzles.com.
This is a pretty minor update. But as some of you may have imagined, the Radiolarian was designed to minimize the star pieces around the corners, in hopes of keeping both the fixed face centers and the corners.
Doing this involves minimizing the star parts on the surface and in the mechanism and then fudging the rest. For folks who have imagined this mechanism, 4 star parts anchor the corner and the 5th interferes. The result works, but turning quality is only poor.