Hi @Akihiko Hoshide
Check the Height property of the Popup widget, it should be auto to fit in and adjust the contents automatically. If any explicit CSS property is added to override the normal height verify that.
Another thing is your using the Popup widget inside Utilities/Align Center, Instead, you can use the Popup widget separately it will appear in the Center of the screen default.
Try following the above methods. Hope it helps!
Regards,
Saravanan Santhanam.