To reproduce:

* Download Tumbleweed Live ISO. Start ISO as usual. Or just use your existing
TW Plasma session post-0531
* Change to Task manager (not icons-only) so that bug is visible
* Open (at least) two apps
* Try to re-arrange them in the Task Manager. It works!
* Log out. Log in to Wayland session.
* Open two apps
* Try to re-arrange them in the Task Manager. It fails.

Now try in Neon. Works in X11 and Wayland sessions. Same Plasma version.

This appears to effect the entire panel, but this is how I noticed the bug, and
a good way to demonstrate it. This is not specific to the Task Manager. You'll
see it when you try it, I'm sure.

Hint to 'control' the behaviour: Drag'n'drop is all messed up, but it appears
that the nature of the issue is that the mouse button release does not return
focus - so, after your drag'n'drop, by clicking somewhere outside the active
elements, you can yank back your focus, and things start to work again.

Hope this Helps!