https://bugs.winehq.org/show_bug.cgi?id=48510
--- Comment #3 from Roman Pišl rpisl@seznam.cz --- Hi, I'm just a fan of Wine (and these programs from 90s bring memories ;-), not a proper developer. From the hotfix it is obvious that the callback is called several times before WM_INITDIALOG is called. And I can't tell whether the hotfix is also the best solution.
I will post this to wine-devel in some time if nobody gives a hint or a better solution. Also mainlining patches takes time anyway..