Few slides show no background in the left scenes menu

I have added pictures as backgrounds (from format background option) in my project and few slides show a white background in the navigation menu present on the left side of the page. These slides show the correct background when I visit the slide but it shows just white in the menu bar as shown in the picture attached. 

Also, the background of these slides takes a second or two to appear when this project is published in the LMS. It looks like there's some latency issue. 

I published the course in HTML5 only format. 

1 Reply