Ha - I was also caught like this and it is a very simple fix and you are going to kick yourself for the answer !!
To get a round button the corner radius you set in your designer must be half the width/height - in other words if your button is 80 x 80 then your corner radius must be 40 to give you a round button !!
In your case - your button is 60 x 60 - so your corner radius must be 30 !!
Ha - I was also caught like this and it is a very simple fix and you are going to kick yourself for the answer !!
To get a round button the corner radius you set in your designer must be half the width/height - in other words if your button is 80 x 80 then your corner radius must be 40 to give you a round button !!
In your case - your button is 60 x 60 - so your corner radius must be 30 !!
You're not wrong. If AutoScaleAll is on and changes the width/height of the button at all.....the corner radius value in the designer won't be exactly half anymore, therefore throwing it off. Setting it in code might be your only option.