Google is showing product rating of 1-star in search results when average rating is 3.7 - 4 stars

[ReachMaineAgency]

When searching for the brand name "SteriPEN", the #3 listing on the SERP is for one of SteriPEN's "Adventurer Opti" product at REI.com,

On the SERP for this search, the REI listing for Adventurer Opti product displays showing the product as 1-star based on a product review from 2010.

What we don't understand is the fact that the product history has a 3.7 to 4.2 rating on most websites. Why would a product with so many reviews and established history have 1 review that drives the 1-star rating from such a prominent retailer?

Makes no sense. Any suggestions as to whom we might be able to contact for help with this is greatly appreciated.

edit?usp=sharing

[WilliamKammer]

It looks like there's a glitch in the markup on the REI website (or whichever 3rd party review software REI uses). Only one of the reviews on the website is being read and put into the snippet on Google. It looks like it might have been the first review given: a 1-star review by "dan hiker" from 4 years ago. Like the markup isn't being automated on each review after that one.

This looks like an issue on REI's side, and not an error with Google.

[ReachMaineAgency]

You are correct. We discovered the pattern across many products not just SteriPEN. Thank you for taking the time to respond.