Google review rating is a ****

My business has been getting numerous 5 star reviews over the past months but my review rating never moves. It is stuck at 4.3. I have lodged numerous disputes and queries with Google but the only response is that they cannot divulge any details about how the score is calculated and that it must be correct. How can over 20 to 25 new 5 star reviews in the past 3 months not create a dent in the rating? This Google rating that so many rely on is a complete farce.