Follow up to my previous post. I did not mention this is on Android v.5.0 tablet. Also, this is a clean "vanilla" MCPE with no packs or more installed. I created a new world from random seed and as soon as I had enough items to fill hotbar it began showing the duplicate items!!! I have screenshots also, but do not see a way to attach them.
I am having this same problem. As stated this only started after update 1.0.7. I have done a backup of my world's, and then a complete uninstall/reinstall of MCPE (uninstall, search for all Mojang directories left and deleted). After reinstall and moving worldview back the bug still occurs. Is there a file in world's directories that controls hotbar???? If so which is it? Can it be cleared or replaced?
Added screen shot 2017-04-22.......... Showing 1 compass in inventory and 2 in hotbar. This is a mild example...Lol. If you throw 1 from hotbar all disappear.