@paul2009 you've just solved the biggest SS problem I've ever encountered! The wrong product image has been showing up on the pages and I've been at my wits end, ready to jump to Shopify over this problem -- no help from SS support, no clue from various online forums, finally found this post and BOOM -- the problem lies in the OPTIONS thumbnail image!! What a super pain in the ass, especially when duplicating items, but now I have the solution and can finally build out the rest of the site. Client will be very relieved and I'll be able to sleep a little better once this nightmare is over. Thank you thank you, I'm bookmarking your services for future needs!
For others who may be searching for this answer, here's a few screenshots showing the problem -- correct images showing in the backend, wrong images showing on the page, happens when duplicating items or when wrong photo is uploaded first -- just delete the thumbnail in OPTIONS and it seems to auto select the first image, as it should be!