Sometimes there are situations where it’s easy for a car seat to accidentally become unbuckled. This is especially true in tight 3-across configurations when a booster/seat belt passenger sits adjacent to the harnessed seat. One low-risk, inexpensive way to prevent this from happening is to use a silicone cupcake liner (or a paper cup) to cover the buckle release button.
Do you have an older child who’s now in a high back booster? Did you know that the way that the seat belt is routed through the booster is essential to how it functions in the event of a crash? Make sure that the seat back is adjusted so that the shoulder belt is coming from above the child’s shoulders.