When you throw item ('q' key) on lower step of a stair,
item bounces on it. In certain condition, item bounces
long time...till it disappears in 5 minutes.

I'll attach sample world data.

In 1.4.2 release, items fall onto lower step of stair, and
you cannot pick up them. This occurs in 1.4.3 prerelease, 1.4.4 release and 1.4.5 release.

Maybe regression of MC-15. And this ticket is duplication of MC-2046 and/or MC-3019.
MC-1720 closed as 'incomplete', so I open this.
Please reopen either and mark this 'duplicate' of it.