Steps to reproduce:
1. Run the attached program and observe the two red circles.
2. Hover mouse over the left circle. Note the odd drawing of the blue stroke. It appears clipped on the sides so the red stroke partially shows.l
3. Hover mouse over the right cirlce. The blue stroke draws properly so no red stroke shows.
The only difference between the two button skin files is that one which draws funny has joints="miter" specified for the SolidColorStroke of the Ellipse. Only the "miter" value has the problem. "round' and "bevel: seem to work properly.