Affects Version/s: 0.12.1 Win10, 0.12.3
Fix Version/s: 0.13.0
Platform:Windows 10 - PC
Steps to duplicate
-Start a creative world.
-Make a portal.
-Place a chest outside the portal.
-Switch to Survival (So that portal transport isn't instant.).
-Just as you get in the portal entrance, open the chest (using either keyboard or mouse), then quickly walk out of portal.
Conclusion The player will not be able to look left or right. Their camera position will be permanently bugged until you pause/unpause the game or open a block UI. Mouse movement appears to be disabled as soon as the player tries to open the chest. Mouse buttons still function. It's always the mouse that is affected, even if you open the chest from the keyboard.
EDIT: This issue affects Minecraft Windows 10 Edition when using a keyboard and mouse.