Sitz Bone Pain Using Gokhale Chair

Hello,

I recently purchased the Gokhale chair and have been very impressed with its quality and design. However, I've started experiencing pain and irritation around my sitz bones while both stretchsitting and stacksitting after using the chair for only a few days.  This has never been an issue for me in any other chair.  Any idea what the issue might be and how I could address it?