The problem appears to be unique to Story skin. So the example you sent (Tiger skin) works fine for me too.
Here's an example using Story vs Tiger.
When I open the first one on Android/Chrome, the Map opens fine, but will time out after 10 seconds. And if I make the map full screen and wait for the timeout, the page is frozen.
The behavior of Tiger on Android/Chrome doesn't have a timeout or fullscreen option, so I don't encounter the issue.
In general, I've found the Map timeout behavior on mobile to be a bit of a nuisance as it seems to happen even when I'm moving around on the Map looking for something, though at least it remembers where I was when I reopen the Map. And of course, the page freezing when Map times out in fullscreen is even more of a nuisance.
Story skin:
https://www.littleofinterest.com/jAlbum-Story-Maps/#img=Bled.jpg
Tiger skin:
https://www.littleofinterest.com/jAlbum-Tiger-Maps/index.html#img=Bled.jpg
Thanks for looking into the Firefox behavior with videos. Does Story have the option to add an 'arrow' to the control bar on mobile devices? I don't really want to have it there, but trying to think of way to handle suchsituations.
Thanks.