Problems playing slideshow video from OneDrive

I uploaded a 3.5 minute MP4 FotoMagico slideshow video with two short embedded videos to OneDrive. When playing, the file crashed at the same place with the message, “sorry there was a problem loading the video”.
I then re-edited the embedded videos, re-loaded them into FotoMagico, re-uploaded the file to OneDrive and now it works.
Then I got cocky and tweaked the FotoMagico file one more time, up-loaded what I thought would be the final version, but now the original bug returned (in a different spot) and it crashed again.
Fortunately I still had the file that worked, so I ended up just using that again. But what could possibly be causing the problem? The upload process? The FotoMagico rendering process? Something random with OneDrive? Any thoughts please? Thanks!

@JimMorin Thank you for using FotoMagico. I’m sorry that you’re experiencing these problems. We will have to investigate more deeply, but my guess would be that OneDrive does some magic with the file system that is unhealthy to FotoMagico. There are sometimes similar problems with files on iCloud and Dropbox and we recommend to copy FotoMagico files to a local file system before working with them.