Unable to set image height to 100% if it is in a stack

Hello,

I have two images and text inside of a stack – image text image --. The stack is set to 100% height (to fill the section). When I click on each image, I am unable to set height to a %. I am only given: Pixels, Viewport Height, Viewport Width, Auto and Calculation. If I remove them from the stack, I am able to set height to a %, but I would like to keep them in a stack.

This is in Wix Studio.

If anyone is able to help it would be greatly appreciated.