Yes, both are buttons and yes, I’m using the hide/show action. And finally I found the mistake – I was working with the appearance of the buttons (in normal mode they are transparent and in mouse above mode they are shown), but also chose “show” in the show/hide-list while rollover, but in the end I had to ignore those in each button, so now it works. It’s working really well in the EPUB Interactivity Preview and it also work in the PDF. But in the PDF it works very incorrect – also after rolloff buttons are still shown though they should be transparent again after rolloff. Seems like it can’t work so fast. Do you have an idea how to make that work better? In the EPUB it’s perfect, but the document has to be an PDF unfortunately.

Thanks a lot for your answer :)