Cannot run two containers simultaneously (using VNC / X server?)

[Snake883]

I can't seem to get two docker containers (connected to the gluetun container) to run at the same time.
I can get only one to run at a time, not simultaneously.
Network ports do not seem to be the problem.
Logs lead me to believe it might have something to do with VNC servers (X server).
Or there's some sort of resource sharing conflict. None of it documented in the containers.

Container: kasmweb/signal: (KASMVNC)

------------------ EXECUTE COMMAND ------------------
Executing command: '/dockerstartup/vnc_startup.sh /dockerstartup/kasm_startup.sh --shm-size=512m --restart=on-failure:1'
2025-11-15T04:37:41Z DEBUG (vnc_startup.sh): KASM_PROFILE_LDR is not set.

---------  purging existing VNC password settings  ---------
2025-11-15T04:37:41Z DEBUG (vnc_startup.sh): Starting KasmVNC
_XSERVTransSocketUNIXCreateListener: ...SocketCreateListener() failed
_XSERVTransMakeAllCOTSServerListeners: server already running
(EE) 
Fatal server error:
(EE) Cannot establish any listening sockets - Make sure an  isn't already running(EE) 

Container: lscr.io/linuxserver/librewolf (Selkies VNC)

_XSERVTransSocketUNIXCreateListener: ...SocketCreateListener() failed
_XSERVTransMakeAllCOTSServerListeners: server already running
(EE) 
Fatal server error:
(EE) Cannot establish any listening sockets - Make sure an X server isn't already running(EE) 
shmdt: Invalid argument
shmdt failed, Invalid argumentINFO:data_websocket:pcmflux library found. Audio capture is available.
INFO:data_websocket:pixelflux library found. Striped encoding modes available.
Traceback (most recent call last):
  File "/lsiopy/bin/selkies", line 8, in <module>
    sys.exit(main())
             ~~~~^^
  File "/lsiopy/lib/python3.13/site-packages/selkies/__main__.py", line 15, in main
    from .selkies import ws_entrypoint
  File "/lsiopy/lib/python3.13/site-packages/selkies/selkies.py", line 96, in <module>
    from .input_handler import WebRTCInput as InputHandler, SelkiesGamepad, GamepadMapper
  File "/lsiopy/lib/python3.13/site-packages/selkies/input_handler.py", line 33, in <module>
    import pynput
  File "/lsiopy/lib/python3.13/site-packages/pynput/__init__.py", line 40, in <module>
    from . import keyboard
  File "/lsiopy/lib/python3.13/site-packages/pynput/keyboard/__init__.py", line 31, in <module>
    backend = backend(__name__)
  File "/lsiopy/lib/python3.13/site-packages/pynput/_util/__init__.py", line 78, in backend
    raise ImportError('this platform is not supported: {}'.format(
    ...<5 lines>...
            if resolutions else '')
ImportError: this platform is not supported: ('failed to acquire X connection: Can\'t connect to display ":1": b\'Authorization required, but no authorization protocol specified\\n\'', DisplayConnectionError(':1', b'Authorization required, but no authorization protocol specified\n'))

Try one of the following resolutions:

 * Please make sure that you have an X server running, and that the DISPLAY environment variable is set correctly
xsettingsd: Loaded 5 settings from /config/.xsettingsd
Authorization required, but no authorization protocol specified