multiple rectangles as buttons - with MouseOver - How to keep MouseOver separated?

Hi all,

It's been a while since I've been working with Xara. Even though much too late I still want to contribute my deepest thoughts of respect to Soquili and his family. A tremendous loss to the community.

Running X9 Pro currently.
I'm setting up a documentation site for which I want to use multiple rectangles layed over a screenshot as buttons linked to their respective page.

My problem is that when MouseOver-ing over 1 singel button, all the other buttons high light or MouseOver also.
So at first I thought maybe I need a separate 'MouseOver' layer per button, but on another page it is working as it should.
Problem is I can't see any difference - Nevertheless the behavior is very different??

Can somebody point out my mistake or help me onwards with this?

Thanks a lot!