The first connection to the login window right after the local user on the Mac has logged out could hang with a white screen visible on the client. Every next connection will hang too but restarting the NoMachine server fixes the problem.

This issue occurs randomly: it occurs often on few machines and very rarely (or never) on most machines.

The following warnings are generally present in the session log on the server:

17898 20739 15:58:45 276.436 MirrorPoller: WARNING! Wrong pixel encoding string in context [C].
17898 20739 15:58:45 276.585 MirrorPoller: WARNING! Failed to get current mode for display 0.