The simplest option is to remove the offending arm- if it's not in the correct parked position? (There are reference markers on the windscreen that show where the wipers should be parked.) You'll most likely need a small two arm puller to get the wiper off the motor spindle. Be aware that the motor will "free wheel" with the ignition off- so double check the motor is properly parked before refitting the arm.
The other option involves performing a wiper motor calibration/ alignment procedure which involves using an OBD2 interface and the free ForScan software. That allows resetting of the maximum wiper position.
Just to check that you have the wipers in the correct order were the driver wiper should be the one that sits above the passenger one. It is easy to muddle up the order and this could the cause after cleaning the car?