Task Manager shows wrong application's icon/title/thumbnail for an unrelated running window

[robinsiebler]

Description

I am developing a Python/Qt6 app. When I launch it, I get the wrong icon in the taskbar. I origanally filed this against KDE, but they resolved it as a Vorta issue.

STEPS TO REPRODUCE

1. Have Vorta (backup tool) running in the background (tray-only, StartupWMClass=python3 per its .desktop file)
2. Launch an unrelated custom Qt/PySide6 application (WM_CLASS "sticky-notes", distinct PID, distinct D-Bus StatusNotifierItem registration)
3. Observe the Task Manager (taskbar)

Observed: A taskbar entry appears labeled "Vorta" with Vorta's icon, but its live thumbnail preview shows the other application's window content. Double-clicking this entry shows/hides the other app's window, not Vorta's — proving the entry is functionally bound to the wrong window.

Additional notes:

Confirmed both apps have fully distinct WM_CLASS, PID, and D-Bus StatusNotifierItem registrations (no collision at that layer)
Persists across a full logout/login (rules out simple stale-cache theory)
Persists even after fully quitting Vorta (rules out a ghost/zombie-window theory — the entry stays bound to the live window)
Removing/re-adding the System Tray widget had no effect (confirms this is the Task Manager widget, not System Tray)
Expected: Each taskbar entry should show the correct title/icon/thumbnail for its own window.

SOFTWARE/OS VERSIONS
Operating System: Nobara Linux 43 (KDE Plasma Desktop Edition),
KDE Plasma Version: Plasma 6.6

Reproduction

• I tried to reproduce the issue.
• I was able to reproduce the issue.

OS

Nobara 43

Version of Vorta

0.11.4

What did you install Vorta with?

Distribution package

Version of Borg

1.4.4

Logs

[gpenz]

Seems like #2535, which is fixed by #2536.
I'm not convinced this bug can be reproduced with any unrelated custom Qt/PySide6 with a distinct WM_CLASS like "sticky-notes" as you say (I can't, on GNOME), but it makes sense that Vorta conflicts with your app as of now.