Layout in campaign reloads after specified duration but doesn't change

I have a campaign with 3 layouts. Every layout a background image and one to two text areas. The layouts have a duration of 5 seconds which is shown on the layouts screen.
The campaign screen shows the campaign as consisting of 3 layouts, with a summarized duration of 15 seconds.

However, the player (windows) shows the following behaviour: showing a layout for 5 seconds. After that, the layout flashes briefly (I suppose, refreshing), then the same layout is shown for 5 seconds again. This repeats a third time, so each layout is shown for 15 seconds, with two flashes in between. After these 15 seconds, the campaign switches to the next layout.

So, my question is, why do these flashes and longer durations occur, while the web frontend shows the desired durations of 5 seconds each?

What CMS and player version are you using please?

Could you show us a screenshot of status window on the player?
(press i on your keyboard while Xibo for Windows has focus)