I was changing out my pokemon using a PC but when I switched out my Lunala it showed a wierd sprite.
I managed to find that if I hold shift and click twice or 3 times, it would put MissingNo. in my pc, it says it's level is -1 and Fainted
when you go onto Stats it completely crashes your minecraft, this also is removed when you leave the game or give it an item,
in some cases it completely wipes your team.

Thanks for the report but iv'e been unable to replicate this with the method you have given,
If possible can you provide a video of this and the crash logs please as while missing no is an error handler it should no be crashing the game from what iv'e heard.