Nvidia Shield K1 tablet, rooted, stock.
If you are using a controller with MCPE, you can't exit the anvil with the b button. The x button at the top right of the screen still works though. Also, I have tested everything and it only applies to the anvil. Rather minor, really.
This is a bulk resolve of issues that haven't been updated to 0.16.0+ yet. Please comment below (To open the ticket) and update your affected versions. If you cannot reproduce the bug, please write in the comments so we can resolve it as "Cannot Reproduce". Thank You!