Bianca M. its something with the video - not entirely sure what though unfortunately. I wish I had better news for you. I would experiment with different exports of that video - webm, uncompressed, different settings etc. Not entirely sure.
the way I know this to be true is that I was able to use that component in a fresh project and I was able to upload like 3-4 random videos into that background spot and they all worked.
Could you please send me some of your random videos? Also, could you share links to your projects? I鈥檇 love to explore the code with the inspector and compare it with mine...