>> But doesn't your Emacs 25 already contain the patch?
 >
 > No. Not if I understand correctly.
 >
 > _My_ Emacs 25.2.rc2 is modified so that the entire body of
 > xg_set_geometry() is deleted and replaced by a call to
 > gtk_window_move(). This fixes the bug and did not produce any
 > adverse effects in six weeks of use (on my system at least).
 >
 > My Emacs 25.2 is the stock release from the tarball. I don't know
 > if it contains any patch for this bug, but if it does that patch
 > does not appear to work.
 >
 >> The only difference I made lately was to set the default value
 >> of ‘x-gtk-use-window-move’ so all you have to do is to make the
 >> last line of your xterm.c read
 >>
 >> x_gtk_use_window_move = true;
 >
 > The symbol `x_gtk_use_window_move' is not defined in the emacs-25
 > branch, only in master.

Sorry.  I forgot to tell you to apply that change to your Emacs 25 back
then.  Please remove any changes I proposed earlier and try to apply the
attached x_gtk_use_window_move.diff to your Emacs 25.

Thanks, martin