Problem with 'isButtonFooterFixed' parameter

I'm geting a problem when using the isButtonFooterFixed paramter in a FormLayout and opening it in a dialog box.

The interface preview is working as expected, when opening the process in a 'NEW_PAGE' is working as expected but if I try to open the interface as a Dialog box it is not fixing the buttons in the bottom part of the modal.

Anyone geting the same issue or knows how to fix it?

Thank you!