Hoppers above brewing stands, don't grab an item from a passing minecart from above, in the game tick when the brewing stand below finishes a brewing process. This affects only one hopper in a line of hoppers, that's why I think it is in only one gametick. The hopper before and after grab the ingredient as intended. This is a huge annoyance when the hopper minecart, distributing the ingredients, contains an exact amount of items, because one brewing stand in an array will brew a wrong potion.

To avoid this issue you have to either leave out a brewing stand, which doesn't look nice in an array, or place another line of hoppers above the hopper line that transfers the items to the brewing stand, which is wasteful.