Setting twice value pcvals.paper_invert in paper_store
void
paper_store (void)
{
pcvals.paper_invert = gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (paper_invert));
pcvals.paper_invert = gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (paper_invert));
pcvals.paper_overlay = gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (paper_overlay));
}
https://gitlab.gnome.org/GNOME/gimp/-/blob/master/plug-ins/gimpressionist/paper.c#L119-124