Xubuntu 18.10 dual monitor problem

[Jeffery Small]

I posted this to the Xubuntu Users mailing list, but I'm also posting to
the developer's list
because I have a suspicion that the problem lies in some change made to the
Xfce code
and someone here might better recognize the problem.

System:
    Machine:    Intel Dual Xeon E5-2630
    OS:           Xubuntu 18.10
    GPU:        Nvidia K4000 GPU
    Monitors:   Dual Planar PX212M 1600x1200 Monitors

Problem:

    System has been running fine for years under all past versions of
    Xubuntu up through 18.04.  The dual monitors are configures without
    Xinerama so that separate desktop sessions with separate panels launch
    on each screen.

    After the recent upgrade to Xubuntu 18.10, the second monitor is not
    being recognized.  There is a display :0.0, but no active display :0.1.

    However, the second monitor is actually active:

      * Upon boot it goes from black to a uniform grey

      * The mouse can travel onto the second screen (pointer visible)
        and keyboard input (e.g., volume keys) are active

      * Xscreensaver displays on both monitors when it goes active


    I have tried to manually start an xfwm4 window manager on the second
    screen, but this is not possible without a defined :0.1 display.

    At the following link I have provided a number of screen shots, config
    file listings, output from relevant commands and log files to explain
    in detail what is (or isn't!) happening:

        http://smallthoughts.com/xfce/xfce.html


Question:

    What changed between Xubuntu 18.04 and 18.10 that is keeping the OS
    from detecting the second screen and configuring it properly and what
    can I do to rectify the problem?  I will provide additional information
    as needed.

    Suggestions are truly appreciated.  Thanks for any help you can offer.
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