Weird behavior when writing a window

[Reeve <rfritchman@xxxxxxxxx>]

I'm working with a customer's service program: it writes a window with
a message subfile and operates properly.

However, when the service program is called and displays the window,
the "background" data changes to the calling program's previous
values.  When the window clears, the correct data displays.  This is
not a data problem in the calling program, although it may be a
display file problem.

The window uses default positioning, RSTDSP(*YES), DFRWRT(*YES),
PUTOVR, and OVERLAY.  I can't identify anything funny in the service
program.

Any ideas?  Today, my brain is doubly taxed.

Thanks,
Reeve