I am also testing some of the files.
I found the same problem.
I used same code as @charco for video.
And I also enable built-in-server in content file type and also In option of built in server.
And also tried dependencies option.
With http and also with force virtualization
But still it show invalid source in .exe
My HTML perfectly work in other browser and internet explorer.
I tried to run again with same file and everything running perfectly fine.
I think the problem is when I start testing first time I made mistake in coding that’s why video was not showing but after I made Changes in HTML code even after that it was showing error.
That time even with right coding it was showing error
But when I created new fresh .hepx file then everything was working fine with no error.