X with mwm: do not see outline of window when moving it on some video drivers

Issue

• We are using the Motif Window Manager (mwm) running on a Linux XDMCP server.
• The .Xdefaults file in the user's home directory does not contain "mwm*moveOpaque: True" and therefore defaults to False.
  The Xorg server is on the Linux desktop. We have tried this on several combinations of graphics hardware and drivers.
  We expect to see the outline of the window when moving (dragging) it. In all cases, we see the 4-arrowed pointer. In some cases, we see the outline of the window and in others we don't.