Description:
I am using a behavior pack to allow large fireballs to be summoned with commands, to be used in functions. I wanted them to be hit by a snowball downward, but they collided with the fireball and the fireball did not move.

Observed Results:
Fireball did not move.

Expected Results:
Snowball causes fireball to be launched downward.

How to reproduce (this doesn't require any add-ons):
1) In survival mode, have a ghast shoot a fireball at you.
2) Get the fireball in a stationary position by using a prepared, active repeating command block to teleport all fireballs to some arbitrary point. [Command: /tp @e[type=fireball] ~ ~2 ~]
3) Return to creative mode and kill the ghast; it is no longer needed.
4) Remove the command block; this will leave a stationary fireball.
5) Run the command "/execute @e[type=fireball] ~ ~ ~ /summon snowball ~ ~0.25 ~"
6) The fireball does not move, contrary to what should be happening.