The car seat harness fails to stay engaged in a safe and secure position. When tightened to the correct position it becomes loose. I contacted Nuna and they advised I should clean the harness adjuster button from debris but I did that and the harness is still coming loose. I dont know how many times my children have been transported while wearing this faulty harness over time since purchasing our seats in 2021 but we are in our vehicle daily so my guess is upwards of 100s of times. The manufacturer refuses to take accountability and recommends we wait indefinitely for a new car seat fabric cover, cleaning kit and instructions to alter the car seat for the purpose of cleaning the harness adjuster button ourselves.