I think you might have some left over functions hanging around in the event graph. When you remove LeapEventInterface from a blueprint that depends on it, it gives you an option to remove them or convert to custom nodes. Then when you add the interface again it will clash since the names are the same.
I recommend starting from a fresh blueprint (copy a character) and add/remove things until you stop getting these errors. I’ve tried but I cannot reproduce it myself, try checking your logs found in {Project Root}/saved/logs. By default the plugin warns you if you have a Leap Controller component, but no interface and having just an interface is harmless as it would simply not cause your events to be called.