This is a strange one. I've tested on my published album on the Internet and also on my local NAS webserver. This problem only seems to happen within Firefox on the Android version. Firefox on iOS and Windows is fined, and so are the other browsers on Android, iOS, and Windows.
Problem: The up button on the index pages does not work; the slide pages are fine. When I tap on the up button nothing happens. I've checked the html being delivered and it's all standard html, nothing funky going on. Well confused!
For once, we're in luck - I'm not confused. I'm virtually certain I know where this is coming from. The tipoff is that if you turn the phone to landscape mode, the icon magically comes to life again (of course, the page looks lousy that way, but it reveals the underlying problem). Does that also fix the problem on your phone?
There are 3 or 4 different ways to tackle this, so I need a little tinker time. I need to make sure that whatever patch I make will take care of all the circumstances that can trigger this.