Okay, so this has happened with me a couple of times (maybe thrice or so) that I can move at the start of the game as a child but after a while I can’t move at all!
I can open the crafting library but nothing else, so I have to often die as a child. Earlier I thought it was a problem with my phone but when it occurred multiple times (and after seeing how other things worked) I thought that this had to be a bug.