This happens 70% of the time. If you first use a spawn egg for a phantom, it will successfully take off. But continuing it, results in the phantoms looking downward thing
There is literally no way to make it go away. It makes that cool ribbon animation as if the trident is actually coming back, but it never reaches your inventory
EDIT: killing all entities removes the effect
/summon phantom ~ ~ ~ {size:x}
where x is any number. Without nbt tag this bug doesn't happen. Also the size tag doesn't effect the size for me, all of them are same sizes regardless of x's value. In other videos I saw the sizes changing, doesn't work for me...