Icon keeps disappearing when changing states on mouseover in "Preview entire project"

Hello, 

please help me with following problems with these icons: 

[SCENE 2] Umetanje stupaca -> [slide 2.2.] Simulacija -> [Layer 2.2.4] Dodan je novi stupac -> Icon 4

 [SCENE 3] Brisanje stupaca -> [slide 3.2.] Simulacija -> [Layer 2.2.3] Izbrisan stupac -> Icon 3 1

[SCENE 5] Brisanje redaka -> [slide 5.2.] Simulacija -> [Layer 2.2.4] Izbrisan redak -> Icon 3 1

THE PROBLEM: 

When I try to preview the entire project, when hovering above icon, it doesn't show Mouseover state and the icon dissapears. All other icons seem to be ok.

I can't reproduce the problem when previewing just the slide, or the scene, it happens only when previewing the whole project. 

HINT - when advancing through slides, you'll have to go through "Video" (f.E. slide 2.1) slides and then in the end click on "hand" icon to enter simulation (f.E. slide 2.2.) and then click where the caption is pointing to forward through layers. 

Thank you for your help,

Branimir