Multiplayer crash, can't load world. "Potential cause: Jumploader"

[Ritopanya]

I'm not very good at writing this but this message came after I accidentally put my friend (the host of the server) into a bot.jar.
He tried to restart the world and manage to get out from the jar but me on the other hand, can't join his server anymore. I still be able to play on single player mode though.

We're using hamachi and we don't really have problem with connection.

crash-2021-03-19_23.58.32-client.txt