What should happen:

Dispensed Splash/Lingering Potions give corresponding effects to nearby mobs

What happens:

Potion dispenses, and has pink particles and no effect is given.

Steps to Reproduce:

Put Potions in dispenser and dispense.

This bug exists in current (as of posting this) snapshot 19w09a and seems to have popped up in snapshot 18w50a.

This bug also affects Lingering potions.

Side Note:

As far as I could tell, there are no direct reports of this bug. If this is incorrect, feel free to delete this.