Not able to adjust the roundness of buttons in Storyline

Hi, is anyone else having any issues with rounded buttons?

When I add them they are not showing with a proper rounded end. When adding a rounded rectangle as a shape, there is a the yellow square that I can slide to amend the level of roundness but for some reason this is not available on a button (which I am pretty sure it used to be).

Attached is a screen shot - button is on the left, regular shape is on the right - as you can see the adjustment option is not available.

Storyline is completely up to date and restarted.

If anyone has any suggestions for how I can amend the shape of my button it would be great.