Dispenser and Dropper shooting out when updated

How to reproduce this bug:
1. place a dispenser with about 64 items in it
2. power it; shoots out one.
3. Place redstone (not connected to the input that is powering the dispenser) or any other block near the diespenser (radius of 2 or 3 blocks)
4. It shoots out another item.

ATTENTION!
screenshot-1.jpg is the bug I'm talking about, not others! Comparators are intended to make constant updates, and dispenser BUD.jpg is acutally not BUD, because the redstone dust is powering the block and that powers the dispenser. I would like to remove the picture but I don't know how and I don't even know if I can.