Exporting slides to video gives black start screen

[judithvg]

What I am making:


A presentation in PPT2016, to be exported as a video file that plays in loop in an other 2016 presentation.

What happens:
The exported video starts with a black screen that is not in the slides, also when I uncheck 'End with black slide' in the advanced options.
So every time the video loops to the beginning, instead of fading smoothly from a light blue screen to a light green screen, I get a fraction of black in between.

My question:
Does anyone know how I can get rid of this black frame?
How I am solving it now is trimming and fading the start of the loop video in the second presentation, but I would like to know if I can avoid the black frame when exporting the slides to video?

Thank you!
Judith.