If you look at the hotbar, there is no three-dot icon for the inventory or touch controls (not PE), it is at the bottom of the screen (not Xbox/PS) and he said he was in 18w06a - a JE snapshot. He might have Win10 edition and made a mistake, but it definitely isn't PE.
Try opening it in a different snapshot, or in 1.12. Also, are any of your other worlds broken like this?
Then it seems to be a world specific bug. I'm not really into the technical side, but maybe it got corrupted in one of the snapshots. There might be a way to fix it, but I don't know. Sorry I couldn't help much!