Minecraft version
1.16.4

Mod version and malilib version
litematica-fabric-1.16.4-0.0.0-dev.20201218.041738, malilib-fabric-1.16.4-0.10.0-dev.21+arne.2.jar

Description of the bug
Every time you join a Minestom server (Minecraft server with only the basics implemented) the client instantly crashes.
Crash report: https://pastebin.com/F4p8eLee

To Reproduce
Create a basic Minestom (https://github.com/Minestom/Minestom) server and join it

It looks like the schematic world is not created for some reason, there must be some difference to the login packets from vanilla, or something similar.
Can you try with this build: https://masa.dy.fi/mcmods/litematica/litematica-fabric-1.16.4-0.0.0-dev.20201225.203013.jar

There is a new option in the Generic category: debugLogging. You should enable that before logging in to that server (for example via Mod Menu).
Then normally you would see something like this in the game console while you are logging in to a world:

[20:31:17] [main/INFO]: (Re-)creating the schematic world...
[20:31:17] [main/INFO]: Schematic world created: fi.dy.masa.litematica.world.WorldSchematic@3bb0a95c

I'm assuming these don't appear for you on that server?

It says (Re-)creating the schematic world... and then crashes: https://pastebin.com/MaKfr5zM