Button Radius and Dynamic Color Change Question

I have a button named Stop, with radius set to 12.

I have a timer running to update layout.

In the timer routine, I have this to change button text and color:

If MediaPlayer1.IsPlaying Then Stop.Color = Colors.Red Else Stop.Color = Colors.Green
If MediaPlayer1.IsPlaying Then Stop.Text = "Stop" Else Stop.Text = "Play"

The color change and text change both work. But the button loses its radius (that is, has square 90 degree corners).

If I remove first line (that changes color), the button behaves correctly (changes the text and retains its radius of 12).

What am I doing incorrectly?

Thanks!



David