Items are randomly dropping. A green indicator builds up from the icon box and pops an item out. See this 'resolved' post, same issue: https://bugs.mojang.com/browse/MCPE-15010

Had this last two versions at least. We only get this on the 2nd PC (SurfacePro 4) connected via LAN to my main PC. They are using Xbone Controller, it also has a touch screen. Nearly everything is default settings.

Very annoying bug. Have to exit game, until it is gone. Sometimes returns quickly.