That was more of a guess as the problem applies to more than one application and I couldn't reproduce the same behaviour with Trinity's twin fork of kwin from KDE 3.5.But trinity loads other frameworks too, so it might apply to other components.
On 2 January 2017 at 17:52, Martin Gräßlin <bugzilla_noreply@kde.org> wrote:

> https://bugs.kde.org/show_bug.cgi?id=374452
> --- Comment #1 from Martin Gräßlin <mgraesslin@kde.org> ---
> Why do you think it's a KWin bug? if the application does not open the window,
> that's primarily the application's fault. The window manager does not interact
> with the systray at all.
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