Shift+Tab / Backtab does not work as hotkey

[Janne Paalijarvi]

I cannot assign Shift+Tab / Backtab hotkeys in KDE. I have used Ctrl+Shift+Tab to switch to previous virtual desktop. However, it is not working anymore. I have made a video demonstration about the problem:
https://www.youtube.com/watch?v=OGoi97UMoxg

Expected things to happen:
After binding Ctrl+Shift+Tab to "Switch to previous Desktop" and using the hotkey, the previous virtual desktop should be shown.

Actual things happening:
After binding Ctrl+Shift+Tab to "Switch to previous Desktop" and using the hotkey, the hotkey does not activate. It looks like the sequence KDE actually sees is Ctrl+Tab, meaning it seems to be ignoring the Shift modifier for some reason.

Information:
Description: Ubuntu 16.04.1 LTS
Release: 16.04

KDE Plasma Version: 5.5.5
Qt version: 5.5.1
Kernel version: 4.4.0-31-generic
OS Type: 64-bit

[Ron HD (ronhd)]

I have the same problem. It was in KDE 5 on PCLinuxOS as well, but there I was able to work around it by manually editing the shortcuts file to say "Ctrl+Shift+Backtab" instead of "Ctrl+Shift+Tab". Apparently, the Shift+Tab was mapped to Backtab, but the Shift modifier was still presented. However, this workaround does not work in Ubuntu.