Items disappearing of droppers in some situations

When Droppers are facing a storage block full of items (or all slots with at least one different item from the type of item that the dropper will drop) and the dropper has more than one of the same item, Droppers will dispense the items making them disappear, and just one of the item will stay in the dropper.

Guess that's it...
Hope it can be understandable, my english is not that good.
Thanks