If the player enters an uloaded chunk above cloud level, they will be stuck in place and jitter about wildly. During this time, the HUD and d-pad are not able to be interacted with.
Tested in creative mode, whilst flying. Prior to 0.9.4 (0.9.3 on Android) there was no barrier preventing the player from entering, and thus this could be reproduced below cloud level (see MCPE-7746).