I want to place down a MarkerPlus on a Sand and then the Game crashes with following Crash Report: https://gist.github.com/DanHCraft/7267acfca15d4513faf824ff9abb5d36#file-crash-2018-03-29_19-18-06-client-txt

Sorry I found the problem by myself:
Sponge have not to be installed on the client.

Thank you for the crash report.
I found a problem that marker called ForgeChunkManager#requestTicket even in client world. Code
Other machine don't call the method on client world. Example

I inserted if(!world.isRemote) to check if server world or not in BlockMarker.java.

Do other blocks work fine without crash?