This morning Tesla announced a voluntary recall of 53,000 vehicles shipped in 2016. Tesla shipped a total of 76,000 vehicles in 2016, so this is a large fraction of the company’s sales for the year.

According to Tesla, a defective part in the parking brake could prevent the brake from releasing. “We do not believe this issue could ever lead to a safety concern for customers and we have not seen a single accident or injury relating to it,” Tesla said in an email statement to Vox. The worst that could happen is that a vehicle could be immobilized by a parking brake that can’t be disengaged.

Still, Tesla is asking customers to get their cars checked out. According to CNBC, Tesla expects the process to take about 45 minutes and that no more than 5 percent of cars actually have the defective component. Tesla says that the supplier of the defective part, Brembo, will be covering the cost of the repairs.

Tesla’s stock value fell about 2 percent after the news broke. The defect will add to questions about the overall reliability of Tesla’s vehicles. Quality control is particularly important for mass-market vehicles like Tesla’s forthcoming Model 3, and critics have questioned whether Tesla can match the high quality standards achieved by incumbent carmakers.