Bizarre Focal screen behavior

[MR ZenWiz]

My partner is running Xubuntu 20.04 on her Dell Inspiron 17"
(1600x900) laptop with an external HDMI monitor (32", 1920x1080).  In
general, the primary display is set to the 32" HDMI monitor and the
laptop is closed (and properly set to run this way).

Every once in a while, seemingly at random, she has this bizarro
display issue where her windows appear as extending below the bottom
of the screen, hiding some of the lower window controls (like the
LibreOffice Writer Print window's Okay and Cancel buttons, sometimes
even the panel across the bottom of her screen) because the window is
too large for the screen.  This even happens when the window is
"maximized" and more often than not this is the case.

I have checked the display settings numerous times, and the screen
sizes are set properly.

This does not happen all the time, just seemingly at random.

The only strange thing I've seen is that, in the display settings, the
laptop screen, when it's open, shows as the upper left 1600x900 area
on top of the 1920x1080 HDMI area.  When the lid is closed, the laptop
display settings are invisible (duh).  I'm wondering if the
system/drivers/something are getting confused about what the correct
display size is.  It looks and behaves that way, but it doesn't show
anything to admit this.

What am I looking for to fix this?

Thanks.

Mark