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.