The Harness Adjuster Strap (item 5 in attached snip from user manual) loosens while in use. This item was manufactured post-recall 24C002000, using Nuna’s new design described here: [XXX] This design change did not prevent the functionality of the strap to fail. There was zero to minimal debris (no food, drink, or water) in the mechanism causing it to fail. The Harness Release button (item 4 in snip from user manual) actuates freely. The adjuster strap, and subsequently the entire harness strap, moves freely, while the carseat is loaded or unloaded. I have a video available showing that the strop in the seat freely moving. We discovered the product failure while loading the child in the carseat and testing it’s security by pulling on chest straps. Nuna’s response was lackluster and unprofessional. Here is the sequence of events: We immediately reported the issue the first business day available, May 27th, and Nuna responded 24hrs later, informing us they would again respond in 1-2 business days to send us a form and shipping label to send back the defective product. We responded the same day asking them to expedite the process and send us a new product immediately as we had no backup for a carseat and my wife could not leave the home. A little over 48 hrs later they denied our request, and sent us the shipping and RMA form. We are now a full business week past the initial request and now are returning the carseat, with no assurance of when the replacement will be delivered. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)