Steps to reproduce:

• Open Minecraft PE
• Open a world
• Hit "Back" on the Android navbar to bring up the pause screen
• Select Options
• Hit "Back" on the Android navbar

Expected:

• Options should close and bring me back to the pause screen

Actual:

• Nothing happens

Interestingly, the back button works on the Options screen if you open it from the main menu (without a world loaded)

Sorry if this is a duplicate.