I was trying to use Command Blocks to get Phantoms to be able to pick you up, to do that, I had a tag called "grab" applied to any player within 3 blocks of a Phantom, and tagged players will be teleported to the nearest Phantom, with a clock attached to a Repeating block that will un-tag players assuming they're currently in the air.
But during testing I tried to sprint jump towards the Phantom to get results quicker and I got a crash screen saying something like "Entity has Invalid Rotation", and being forced back into the multiplayer menu even though I was in a single-player world.
Unfortunately I can't re-create that specific screen since it just crashes when I try to re-enter that world, but instead gives me this crash report in the launcher!