My function keys in Outlook have shifted five keys to the right. For example, if I assign Ctrl + F2 as the shortcut for one of the color categories, then the actual working shortcut is Ctrl + F7. Also, the shortcut for toggling the ribbon would normally be Ctrl + F1, but here I have to use Ctrl + F6. It only seems to affect the function keys when the shortcut uses a combination of Ctrl and F# - the function keys work fine on their own, for example F1 for help, F3 to search, and so on.
This issue has been found on multiple machines (one running Outlook 2013, and two running 2016).
The function keys work as normal in all other applications, including other Office programs.
What could cause this?