Formatting Page Navigator Buttons

Hello,

I have a problem with formatting Page Navigator buttons avalable as a default navigation tool here:

In Format Navigator panel, there are the options where you can set specific colors depending on stae (default, hover, on press, selected). I did it as I wanted and everything looks as I wanted:

But, there is a strange black frame appearing on clicking the button:

I cannot find any option in Format Navigator panel to get rid of this black rectangular frame.

Existing “outline” option refers only to pentagonal button shape, and it is not black.

Has anybody met this issue?

Regards,

Dariusz