The harness on one of our 2 Nuna Rava carseats affected by the recall has come loose without pressing the harness release on two occasions, failing to restrain my child. I became aware on these two occasions because he was able to lean forward while the car was moving. There was no predictable indicator. Of note I do tighten and release the harness every time I take my kids in and out of the car so there is significant regular movement of the strap. The harness seemed to work between the two instances that occurred a few days apart and seemed to work until I learned of the recall and discontinued use. When I test it manually now the harness holds. As part of the recall have performed the harness test, cleaning, and repeated harness test according to the instructions from Nuna and had a virtual meeting to review the steps. I have expressed concern that through a very small opening under the vehicle belt securement compartment the harness path is partially visible and I can see debris in both seats that I am not able to reach to remove. Of note my son has also vomited and it dripped into the shell in that area and I contacted the support chat and was told to spray enzyme cleaner and allow it to dry. I was advised this area of the seat is not part of the recall and that as long as the teeth of the clip are clean the recall issue has been remedied. I am concerned that with the movement of the strap loosening and tightening the harnesses and movement/vibration of the car this debris could get caught and be the cause of the strap having failed intermittently and more importantly potentially cause it to fail in the future. Safety risk is inadequate restraint of my child. The seat has not been inspected by the manufacturer in person, I explained that i am not comfortable using them and that I want them to provide cleaning but they offered the virtual call instead and I am now waiting for a Nuna car seat tech to contact me regarding my concerns.