Hi, My name is Ross and i will help with this problem. This car has a parking light function, if the indicator switch is left up or down, the right or left side lights will stay switched on, this is for when parking on the side of the road. Often customers complain about this, when they have simply indicated to park and switched the ignition off with the indicator still switched on, it then keeps the side lights on just one side. You may know this and there is a fault, however i have to check this is not the case before i continue. Please let me know if you do need further assistance, or would like me to expand, if you can confirm its not the parking light function doing this, i will continue diagnostics with you, thanks. Ross.