Duplication Glitch

I found a very strange bug and maybe it hasn't been fixed yet, namely the duplication bug 

I found it in Minecraft Pocket Edition 

the bug works inside Beacon and uses pocket UI 
and for example I have one diamond and put the item on the hotbar then I use the Beacon and press the item repeatedly then the item will add itself 

however it only works in Pocket Edition and use Pocket UI

 so I ask Mojang for help to fix the bug because it reduces the fun of playing
and if it's a feature then please delete it but if it's a bug then please fix it