I looked through old bug reports, and it seems like this used to be an issue in 2014 in the Java Edition. I can't summon wither skulls (wither_skull), blue wither skulls (wither_skull_dangerous) or any type of fireball (small_fireball and large_fireball) using command blocks or the in-game chat. This is preventing me from completing a game I'm trying to create and I'm not sure if anyone has realised that this is even an issue yet.
Comments 5
In Java Minecraft, summoning fireballs or wither skulls requires direction NBT data to summon (the Java Minecraft report referring to it here: MC-86011). Without it, the game returns an error message. That type of command would look like this: "/summon fireball ~ ~ ~ {direction:[0.0,0.0,0.0]}".
Unfortunately, Bedrock Minecraft doesn't allow NBT in commands, making it impossible to manually spawn. A fix would be to make the command spawn the fireball or wither skull with the direction tags set to zero by default, or to allow NBT tags in commands.
Cleaning up old tickets: This ticket has not been updated recently (~1 year+) so is being closed as Cannot Reproduce. If you feel this is still a valid issue then please comment, or create a new ticket following the Issue Guidelines.
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There is still an issue, but this is probably WAI (see MCPE-44870)
My friend had a problem similar to yours. The workaround he found was to naturally summon a fireball/skull from the ghast/wither and then run the command while the projectile is near you. Let me know if this helped! 🙂