Why do so many smart CO detectors have mixed Amazon ratings?

Across the reviewers we read, the recurring pain points are app setup friction, occasional chirping that's hard to diagnose, and false low-battery warnings, not sensor failures. r/firealarms commenters also note that Kidde has had quality-control complaints in recent years. Cross-checking expert reviews against verified-purchase Best Buy and Costco reviews gives a more reliable picture than the Amazon star average alone.