If you press Cmd-V, you get content pasted twice. If you press Cmd-Z, you undo two things. There may be more instances of this. I suspect the problem is that RichTextFX has a intrinsic binding for these actions, and we are adding another (menu accelerator?), and then they are both triggering. This is on Mac, but it's worth checking on Windows before fixing. I suspect the fix is either to try to disable/override RichTextFX's binding or remove our accelerator for the action.