I noticed that my rating went up late week to a full five stars after getting a number of great reviews . But a few days ago it went back down to 4.9 without me getting a bad review. I just left some reviews on a bunch of orders, around 7 and it went back up to 5 stars but when I refreshed the page It went right back down to 4.9 again.
That fluctuates depending on the math involved. It depends on total number of reviews and total number of stars, which is 15 for each review, if you get a 5 star review. You would need to calculate the math constantly by adding up all the stars for 60 days and dividing by number of reviews.
I have done that several times and it’s really the only way to get a good understanding of why it keeps changing. I don’t know why just refreshing the page would make it drop. It might have rounded off a review, which it does sometimes.
This gentleman has a good explanation of why the fluctuation happens.