https://bugs.winehq.org/show_bug.cgi?id=45385
--- Comment #2 from John Found johnfound@asm32.info --- I have found a workaround. At first, I am testing under XFCE. There are two options in the "Windows manager tweaks" settings applet:
[ ] Activate focus stealing protection [ ] Honor ICCCM focus hint
So, I have discovered that the bug manifests itself only when both settings are switched ON. Unchecking any of them makes the bug to disappear.
Still it is not very clear where is the bug actually - in the code of the XFCE WM or in WINE. Any ideas about future testing/diagnostics are welcome.