Windshield wiper arm on 2004 Chevrolet Impala

The driver's side wiper arm on occasion will go completely off the glass and over to the side view mirror. What's the cause and what's the fix? Despite the fact that the nut on the wiper blade arm is tight, it continues to happen.

1 answer
Where the wiper arm connects to the wiper motor there is a splined shaft and usually the wiper arm side gets stripped and will need to be replaced.