Nuna Baby Essentials has recalled more than 600,000 child car seats because of issues with a plastic harness adjuster button.The recall involves RAVA models manufactured between 2016 and 2023. "The defect is a result of debris entering the area where the front harness adjuster is located," the company said in documents filed with the National Highway Traffic Safety Administration. "The debris may cause the teeth of the adjuster mechanism to no longer properly clamp onto the adjuster strap, resulting in the harness no longer remaining tight."The NHTSA warns that a child may not remain properly restrained in the event of a crash, increasing the risk of injury.RELATED STORY | Lay's potato chips recalled in these states over 'life-threatening' allergy riskNuna said it will provide customers with a free kit, which includes a new seat pad and instructions to properly clean the harness adjuster area."We are committed to ensuring the highest safety standards, which is why we are taking this proactive step," Nuna said in a statement on its website. The company will contact registered owners about receiving the free kit. Unregistered owners can fill out a form on the company's website to receive the kit. RELATED STORY | Kirkland-brand eggs sold at Costco recalled over salmonella concerns