UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.81 Safari/537.36

Steps to reproduce the problem:
1. KDE with 3 activities
2. a Chrome window with multiple tabs
3. drag-n-drop the active tab to the window border (left or right)
4. KDE switches activities (most of the time)

What is the expected behavior?
It should stay on the current activity

What went wrong?
When I drag a window, KDE doesn't switch activities, only when I drag a browsers tab. 
I'm not aware of any such KDE setting to enable/disable such a behavior and I don't see why it should behave that way for tabs if it doesn't for windows. 

Did this work before? N/A 

Chrome version: 58.0.3029.81  Channel: stable
OS Version: Linux zdev 4.9.0-2-amd64 #1 SMP Debian 4.9.18-1 (2017-03-30) x86_64 GNU/Linux
Flash Version: Shockwave Flash 25.0 r0

My KDE desktop is keeping forgetting all desktop widgets since I first accidentally switched activities the way described above.
Now, when I add a widget and switch to another activity and back the widget is gone.