In my system turn on "Track file transfers and other jobs".
Now when I copy files, plasmashell freeze until ready notification with details.
If files not so much, it very fast. Unnoticeably.
But when it is large dirs or hundred files, plasma freeze up to 30 seconds and more.
Other program work normally, no load on CPU or something.
I'm using Manjaro. But I heard about it bug from other users.
So I decide create bug.
I found something similar https://bugs.kde.org/show_bug.cgi?id=346758
but it closed
Also after freeze, in notification history, I can see empty notification about copy file status... but files copy ready while plasma freezing.
*** This bug has been marked as a duplicate of bug 358231 ***