Reply To: Serve Scaled Images (use smaller images as thumbnails)

Possible solutions, which I havnt tried:
http://wpquestions.com/question/showChrono/id/8850
https://theme-fusion.com/knowledgebase/how-to-fix-woocommerce-image-size-issues/

Info:
https://docs.woocommerce.com/document/using-the-appropriate-product-image-dimensions/