While this probably won't affect many people - it affects my workflow often.

It's not really a bug - more of an annoyance/display issue.

I'm a web developer and often during dev work, there will be multiple instances of IIS express (web server), started and stopped. During this process, the instance/process will often be killed but the system tray icon remains. So you will see duplicate icons showing in the system tray.

When you hover over the top of the icon, windows realises that the process is no longer active and removes the icon from the tray.

The issue is, display fusion keeps that icon active when you hover using a display-fusion taskbar. Left/right clicks do nothing on the inactive icon. Once it's hovered on the windows taskbar side, the icon disappears on both taskbars.

So I guess the "fix" to this issue is: on hover of taskbar icons - check to see if the process is still valid, or optionally do this on-click.