Odd indeed. But thanks for the feedback, it might help the community for some of their own projects.
Videos are a topic on its own and I try to avoid it whenever I can. So I don’t have any advanced knowledge about it.
Are you talking about mobile browsers in genereal or do you refer to a specific OS?
As mentioned above, I didn’t experience any issues when I tested your site with my device.
Can you exclude any hosting issues, since it is self-hosted?
Could you also elobarate, what conclusion Thanasis has reached?
Reducing the video size might solve the issue, but I doubt it is the actual problem here. Of course I can be totally wrong here.