When I wanted to have fun using the levitation effect I was confused because nothing was happening except "this entity could not be found" was appearing, in the chat. I was very confused so I decided to spawn a lot of entitys and apply it to all of them still nothing happened so I spawned more in this time babies were in the group. Whenever I ran the command only the babies began to levitate! I tried this with other effects and I found that the samething happened, and I tried using other versions of the snapshot but they behaved just fine! I hope you find this helpful and resolve this in the next snapshot, thank you. (I was using:/effect @e[type=!Player] minecraft:levitation 100 10)