I’m hoping someone has some insight into this issue I am having. When my 2009 Ranger Sport is parked with engine off, key out and headlights switched off my headlights are turning on and off.

would this be a failing part or water getting in somewhere?

 

It sounds like everything should be going to sleep under those conditions, except perhaps an alarm system. Do you have any aftermarket additions to your electronics, like an aftermarket alarm system or a remote start system? If so try disconnecting them to see if the problem goes away. My wild guess is something that is awake with the switch off, has a ground problem and is using the headlight circuit for it's ground.