When the car is parked and you leave it and come back later the back-up lights are on . The ignition switch is turned off . It does not do it every time it is parked

That just don't make any sense.. Maybe someone has had a similar problem and can shed some light on it.. I've been doing auto repair 43 + years... Never had that problem on one.. Anythings possible given the right circumstances I suppose... 'Something' is shorting the reverse lights to battery power, that is NOT switched! .. Possibly in trailer wiring,, if applicable.. Good luck with it..