Brewing stand not able to receive a drop

Hi, 

When i try to drop with a hopper an item like the blaze powder it doesn't go on the right place(ex:blaze powder going into the ingredient place instead of the blaze powder place) And that's not all because when i try to drop a water flask it doesn't work the water flask stay in the hopper. So please help it's very annoying to make a perfectly automatic potions machine