@tomendop see documentation for "Layout QML Type". It states:
Note: It is not recommended to have bindings to the x, y, width, or height properties of items in a layout, since this would conflict with the goals of Layout, and can also cause binding loops.
I can't say exactly what is going wrong in your example, but it is basically that you are doing something you aren't supposed to do when you choose to use the Layout mechanism.
I think it can be quite confusing as QML has a number of different ways to manage layout and it isn't always obvious which way is best or most appropriate.