Item not flying up glass bug

So when items get stuck in a 3x3 area of glass it should just fly up.l
Like in Xbox and pc
But when I do this on pocket edition the items lag like crazy
How to reproduce this bug
1. Get a 3x3 piper of glass
2. Break the two bottom block of glass
3. Throw items in then quickly put the glass back and then you see the items lagging.