On Wed July 24 2019 23:36:42 J Leslie Turriff wrote:
> > $ ps ufax | grep tdesu

Unfortunately that doesn't show the user running /usr/bin/X11/su.

However it seems possible that your su has lost its suid bit.

Please do "ls -dl /usr/bin/X11 /usr/bin/X11/su /bin/su /usr/bin/su".
(probably one of those files will be missing but that's OK.)

--Mike