I can confirm this problem, but not for all projects. Everything exports fine to HTML5 (looks great!) but video export to any format gives me a static first image all the way through. I’ve been through lots of the presets to no avail.
The project is made up of a tiled PNG world map background (indexed single colour - black only, transparent background, overall opacity reduced in Express Animate) which scrolls horizontally for the duration of the project, and a couple of square PNG icons. I also have a couple of sub-compositions containing a semi-transparent panel and some text, that fade in, hang around for a bit, then fade out again.
The first project I created was a simple “Hello World” where the words “Hello” and “World” slide in, and an underline spreads out beneath the text. That exports fine to both video and HTML5. Perhaps my images were too high resolution for the exporter to handle.
PNG or JPG slide output does work quite well, although you do then have to post-process with ffmpeg or similar, but that introduces its own problems…