[X2Go-User] X applications fail after su - on x2go connection

When I am connected to a Debian server through x2go, my X applications work. When I su - user2 then try any X application they don't work. For example emacs will start in terminal mode and java applications give errors such as java.lang.InternalError: Can't connect to X11 window server using ':52' as the value of the DISPLAY variable

When I echo $DISPLAY before the su -, :52 is the correct display.

I have several other machines that do not have this problem. How do I fix it so that X works through x2go after su -.