I have been trying to make a boss with only command blocks, I made it teleport if you go too far away from it, I wanted to make it fly so I used a phantom, I realized that the phantom got stuck sometimes so I started debugging and found out that if the phantom is charging into you and you teleport it (at least to the player as far as i know) it gets stuck in place and can't move.

Probably important: After viewing the NBT with the /data command i realized that in Motion the Z motion was NaN after setting the nbt to [0.0,0.0,0.0] while the phantom is not attacking it gets fixed.

it also has nothing to do with commands because even after disabling the teleport it keeps happening

The phantom is invisible in the image but i dont think invisibility it has anything to do with it