Hoppers don't let water bottles flow into a brewingstand

 I made an automatic brewingstand and I expected it keep brewing new potions.

But after one set of potions the brewingstand don't let more waterbottles fill the system. and if you leave the world and come back it will do one set again.

the potions get removed but no waterbottle come new in

1. Place a brewingstand 1 block in the sky
2. Place a hopper next to the brewingstand that is facing into it
3. Fill all of them with water bottles
4. Brew a potion
5. Place a hopper below the brewingstand