Maintenance of a Motor Vehicle on a Homeowners Policy

Insured girlfriend's mother was visiting the insured and pulled her auto into insured driveway. The girlfriend's mother asked the insured to change her windshield wiper. Insured was changing the wiper and the blade slipped and struck the windshield breaking the glass. Insured is making a claim under his homeowner policy to pay for the broken windshield.

Question: Does the policy grant coverage for this loss? The insured policy defines motor vehicle liability as maintenance of such vehicle by any person. In this case, insured was maintaining the vehicle. The property damage to others incidental coverage also excludes maintenance of a motor vehicle.