Nxagent fixed by unset LD_LIBRARY_PATH which was set to 
/usr/lib/x86_64-linux-gnu

root@test-triolet:~# nxagent -ac :1

NXAGENT - Version 3.5.99.16

Copyright (c) 2001, 2011 NoMachine (http://www.nomachine.com)
Copyright (c) 2008-2014 Oleksandr Shneyder <o.shneyder@phoca-gmbh.de>
Copyright (c) 2011-2016 Mike Gabriel <mike.gabriel@das-netzwerkteam.de>
Copyright (c) 2014-2016 Ulrich Sibiller <uli42@gmx.de>
Copyright (c) 2014-2016 Mihai Moldovan <ionic@ionic.de>
Copyright (c) 2015-2016 Qindel Group (http://www.qindel.com)
See https://github.com/ArcticaProject/nx-libs for more information.

Info: Agent running with pid '8762'.
Session: Starting session at 'Thu May 24 09:38:15 2018'.
Info: Using alpha channel in render extension.
nxagent: ../../src/xcb_io.c:520: _XAllocID: Assertion `ret != inval_id' 
failed.
Abandon (core dumped)

root@test-triolet:~# unset $LD_LIBRARY_PATH

root@test-triolet:~# nxagent -ac :1

NXAGENT - Version 3.5.99.16

Copyright (c) 2001, 2011 NoMachine (http://www.nomachine.com)
Copyright (c) 2008-2014 Oleksandr Shneyder <o.shneyder@phoca-gmbh.de>
Copyright (c) 2011-2016 Mike Gabriel <mike.gabriel@das-netzwerkteam.de>
Copyright (c) 2014-2016 Ulrich Sibiller <uli42@gmx.de>
Copyright (c) 2014-2016 Mihai Moldovan <ionic@ionic.de>
Copyright (c) 2015-2016 Qindel Group (http://www.qindel.com)
See https://github.com/ArcticaProject/nx-libs for more information.

Info: Agent running with pid '1265'.
Session: Starting session at 'Thu May 24 09:43:02 2018'.
Info: Using alpha channel in render extension.
Info: Not using local device configuration changes.
Warning: Cannot read keystroke file '/root/.nx/config/keystrokes.cfg'.
Info: using keystrokes file '/etc/nxagent/keystrokes.cfg'
Warning: ignoring keystroke 'viewport_scroll_up' (already in use by 
'viewport_move_up')
Warning: ignoring keystroke 'viewport_scroll_up' (already in use by 
'viewport_move_up')
Warning: ignoring keystroke 'viewport_scroll_right' (already in use by 
'viewport_move_right')
Warning: ignoring keystroke 'viewport_scroll_right' (already in use by 
'viewport_move_right')
Warning: ignoring keystroke 'viewport_scroll_down' (already in use by 
'viewport_move_down')
Warning: ignoring keystroke 'viewport_scroll_down' (already in use by 
'viewport_move_down')
Current known keystrokes:
   close_session         Ctrl+Alt+t
   switch_all_screens    Ctrl+Alt+f
   fullscreen            Ctrl+Shift+Alt+f
   minimize              Ctrl+Alt+m
   defer                 Ctrl+Alt+e
   ignore                Ctrl+Alt+BackSpace
   force_synchronization Ctrl+Alt+j
   resize                Ctrl+Alt+r
   viewport_move_left    Ctrl+Shift+Alt+Left
   viewport_move_left    Ctrl+Shift+Alt+KP_Left
   viewport_move_up      Ctrl+Alt+Up
   viewport_move_up      Ctrl+Alt+KP_Up
   viewport_move_right   Ctrl+Alt+Right
   viewport_move_right   Ctrl+Alt+KP_Right
   viewport_move_down    Ctrl+Alt+Down
   viewport_move_down    Ctrl+Alt+KP_Down
   viewport_scroll_left  Ctrl+Alt+Left
   viewport_scroll_left  Ctrl+Alt+KP_Left
   reread_keystrokes     Ctrl+Alt+k
Warning: SessionPath not defined
Info: Keycode conversion auto-determined as on
     xkb_keycodes             { include "xfree86+aliases(qwerty)" };
     xkb_types                { include "complete" };
     xkb_compatibility        { include "complete" };
     xkb_symbols              { include "pc+us" };
     xkb_geometry             { include "pc(pc102)" };
The XKEYBOARD keymap compiler (xkbcomp) reports:
 > Error:            Cannot open "compiled/server-1.xkm" to write 
keyboard description
 >                   Exiting
Session: Session started at 'Thu May 24 09:43:03 2018'.
Info: Screen [0] resized to geometry [958x383] fullscreen [0].
^CSession: Terminating session at 'Thu May 24 09:43:04 2018'.
Session: Session terminated at 'Thu May 24 09:43:04 2018'.
FreeFontPath: FPE "/usr/share/fonts/X11/misc/" refcount is 2, should be 
1; fixing.