Just ran into this myself and fixed it just by nesting the content in the right configuration of widgets. It took a minute to figure out the exact combination of settings so I figured I could share some screenshots to help
Scale box: set Stretch to Scale to Fit and Stretch Direction to Both
Size box: set horizontal and vertical alignment to “fit”, and set Mix/Max Aspect Ratio to the intended value
Content (this could also be an Overlay to nest other children, I’m just using an image): set horizontal and vertical alignment to “fit”
