Ctrl + Shift + Tab Not Working in Safari or Chromium

I tried in a Chromium browser and Safari, the shortcut mapped to Ctrl + Shift + Tab is not working.

Nothing happens.

Ctrl + Tab works fine for navigating between two windows in KM. Doing the shortcut without KM works fine and I can shuffle back through my tabs.

Any suggestions on why it may not be working or a possible solution?

Here is my config:

In Safari, Control-Shift-Tab appears to map to the Window ➤ Show Previous Tab menu.