Provide at least the following information

• Minecraft version
  1.21.4
• Mod version and malilib version
  Litematica 0.21.1 and MaLiLib 0.23.1
• A clear description of the issue
  When joining a Minecraft network that uses Velocity (https://github.com/PaperMC/Velocity) as a proxy and Sonar as an anti bot system (https://github.com/jonesdevelopment/sonar), any client with Litematica on it crashes. After you successfully make it through the verification, you're able to log on even with the mod because Sonar keeps a record of IP+user combinations which further proves that it's this exact combination which Litematica to crash.
  
  I also have a client crash log of when it happens: https://mclo.gs/xlVnziF
  
  If any further information is required, please let me know.

One of the latter updates of Sonar seems to have fixed this issue so I'll be closing this ticket.