The DISPLAY environment variable is used on Linux and macOS by some NoMachine components to verify if there are available connections to a local X server. If the variable is wrong (e.g. it does point to a not existing unix socket), a NoMachine library aborts causing the client to close suddenly.

As a workaround, fix the DISPLAY variable to point the right socket.

A similar problem occurs on Windows when the DISPLAY variable -which is not needed by NoMachine- is set on the system for some reasons. In this case, simply remove or rename it.