[X2Go-User] x2go session crashes xfwm4

I've recently upgraded my system to xubuntu 20.10 and x2go sessions now crash the xfwm4 window manager. After restarting xfwm4 from a terminal window I see the following crash report when I run another x2go session:-

xfwm4:15183): Gdk-ERROR **: 11:27:33.867: The program 'xfwm4' received
an X Window System error.
This probably reflects a bug in the program.
The error was 'XSyncBadAlarm'.
  (Details: serial 213260 error_code 135 request_code 134 (SYNC) minor_code 11)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the GDK_SYNCHRONIZE environment
   variable to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)
Trace/breakpoint trap (core dumped)

Is this a bug in xfwm4 or in x2go?

-- Chris Green