In a fresh Ubuntu Budgie 21.10 installation I position the top panel to the right. When I maximize an application its window takes all of the remaining width - as expected.
In a next step I enable fractional scaling and set it to 125%. When I do now maximize an application its window takes the complete screen width. It is located behind the panel. This is unexpected.
Disabling fractional scaling makes it work again.
Can anyone reproduce this behaviour?