Problem when using the command / morph morph "players" "mob": the server crashes and I must delete the info of the player targeted by the command so that he can return to the server without crashing

As Morph has just been rewritten and released for MC 1.16.5, I am clearing the issue tracker as I have not provided any support Morph for 1.12.2 and earlier. My apologies for not addressing your issue.