The following behaviour has been reproduced on Manjaro with XFCE as desktop environment.

When user connects to the physical desktop by NoMachine and presses the CTRL+SUPER key combination, the NoMachine session freezes because the X server suddenly terminates on Manjaro. This doesn't happen if the user is logged into the desktop locally and presses CTRL+SUPER. 

As a workaround, restart lightdm from a terminal:

systemctl restart lightdm

This will start a new X server and restore the ability to interact with the desktop without disconnecting the NoMachine session.

Steps to reproduce:

1. Download and install Manjaro XFCE (not lite) from https://manjaro.org/downloads/official/xfce/

2. Install NoMachine free edition on Manjaro

3. Enable "Grab the keyboard input" in the player settings.

4. Connect from Windows to the XFCE physical desktop on Manjaro

5. Press the CTRL+SUPER key combination: the NoMachine session becomes unresponsive and the UI on Manjaro suddenly terminates.