Blank parts of video start black then white

In my video project, I have one audio track and one video track.

The video track has several sections without media.

When I exported the project, the first half of the exported video is what I expected. Plain black during the sections without media. However, nearer to the end of the exported video, instead of plain black, it’s plain white during the sections without media.

blank%20space%20clips
Works fine here.
No filters.
Blank spaces are black.
Shotcut Version 18.08.01
Windows 10 Home. 64 Bit