I'm having a strange problem with Terminator:
The keyboard shortcuts work for the default keyboard layout (in my case, German) just fine.
But when I switch the keyboard layout using Super+Space (to Polish or English-US), they don't work any more.
Instead, e.g. Ctrl+Shift+O sends Return to the terminal.
The only shortcuts that work seem to be F11 for fullscreen and Ctrl+Shift+T for new tab.
The problem seems to concern the functionality, not the key combination:
I remapped horizontal split on F11 or Ctrl+Shift+T, and it still didn't work, while after remapping new tab to Ctrl+Shift+O, it still worked.
I'm using Ubuntu GNOME 16.4. Keyboard shortcuts in other applications work without problems.
EDIT: Tried also switching the default keyboard layout to Polish.
Now the shortcuts work for Polish layout but not for German, so it's the matter of default/non-default, regardless of the actual layout.
Best Answer
This also might be because you have german keyboard which physical layout is different than US or polish (for example the ? symbol on US software layout on nordic and German keyboards is typed by holding shift and pressing - symbol.
All regional keyboards have different layouts (with exception of modifier, function, cursor, system command and numeric keys)
Here is example of US keyboard layout