I will be playing on a world and once in a while, usually if players are on it, it will completely bug out for 1-2 minutes. Basically, entities and chunks may fail to render properly and stuff. I thing what's happening is the game doesn't actually allow you to move but the camera can still move, because if I type /tp @s I get teleported somewhere else. I think there might be more to it though because the other players online will complain about lag while it's happening but I could not identify what type of lag they were experiencing. I can't really provide a picture or a video as of right now but I may provide one in the future if it still happens. The only thing I have found that will usually stop it immediately is to switch your gamemode to Survival and type /kill (my world has Keep Inventory on). You can't do much of anything at all while it's happening. I don't know if it only occurs on iOS or not.