Scaling text uniformly within a symbol button

Hi,

basic question but I'm follwing an Adobe Animate tutorial and creating a button with text but when i scale the button in the scene, it scales the text non-uniformly whereas in the tutorial, it's holding the correct scaling and not distorting.

The button is drawn then saved as a moviel clip symbol then after double clicking it's symbol in the library and entering the edit mode, I add static text and position within the button. I then exit to the stage and try to scale to fit the scene but it's distorting the text. I can't see any stage I've missed and if I import their scene (Lynda.com), the button text scales as it should, I must be missing something obvious!

Any help would be much appreciated

Thanks

Dan