Kate 3.14.1 (x86_64-linux-gnu-gcc) after upgrade of KUbuntu to Linux (x86_64) release 3.16.0-26-generic changes from being on one desktop workspace to all workspaces when you close down the desktop. 
I noticed it on re-start-up, but have halted the shutdown and found it happens before the system is closed down. Worked before the kernal upgrade and doesn't appear on other applications (like Firefox) although I have not specifically tested any other KDE applications ( I could do so if required). I don't know if Kate was upgraded recently.

Reproducible: Always

Steps to Reproduce:
1. Have open applications and Kate open on Workspace X
2. Close down the system
3. Halt close down or restart after closedown
4. Kate appears on every Workspace.
5. Right click on title bar, click move to desktop, check menu, all desktops is now checked.

Actual Results:  
As above, but I then have to right click title bar to reset Kate to it's single desktop.
It does not work in veverse, if you close down then cancel, on all desktops Kate remains on all desktops.

Expected Results:  
Kate closes down, then reopens when you start the system, on the Desktop you left it on and with all your open files available.

It's an annoying bug, to have to go through the operation of changeing the desktop setting, after restarting the system. It has spoilt a usefull and energy efficient feature of being able to shut the system with confidence any open work will be retained on start-up. 

I was finding it a very usefull feature, as a disabled person on low income, to know I could close the computer and restart where I left it. I have lost some confidence in that due to the bug.

It might indicate other problems. It may be indicating a kernal incompatibility.

It makes Kate and KUbuntu look unproffesional. I have therefore marked it as a major bug.