I just switched over from Wix and while I'm happy with a lot of aspects of Shopify, when something goes wrong, it seems to REALLY go wrong.
I am using the Galleria theme. I have over 50 products, all garments, which have 6 or more variations for sizing, usually. (XS-2XL)
No matter what size is selected, when you add it to the cart, it changes to XS. It doesn't happen to all the products on the entire site, and I don't see any relevant pattern to the garments that it does happen to.
So I've already had several customers email me saying they didn't order that size. Now I have to 2nd guess and double check with each customer what size they meant to order. It's very time consuming and unprofessional.
After a bunch of support tickets to Shopify and the makers of the Galleria theme, they figured out it was something in the 3rd party reviews app that was messing up the code so I reached out to them too and something one of the three of them worked.
I’ve found that there’s a lot Shopify add-ons that conflict with each other for no good reason.