Amazon calculates a product's star ratings based on a machine learned model instead of a raw data average. The model takes into account factors including the age of a rating, whether the ratings are from verified purchasers and factors that establish reviewer trustworthiness.
Bought once defective, was late to return it. Bought again, it was defective. requested replacement, that was also defective. I don't understand why Amazon is not removing this type of supplier and shady vendor.