The highlighted bit, is the issue.
It's not just cases of sending wrong items, not having stock of replacements, etc. - those things happen to all retail shops, and the number of happy customers outweigh the ones that have these sorts of issues - that is fine.
It's how Evetech responds when something goes wrong and it's their own fault that is the problem. They do not try their best to rectify it. They rectify it by means that leave the customer worse off than when they started, instead of putting the customer in the same position as when the item was purchased.
Recent examples include refusing refunds, refunding in store credit that expires in 90 days and can't be paid out in cash, refunding smaller amounts than the original purchase price due to "depreciation," blaming the customer for issues they themselves caused, and any number of other issues.
While other retail outlets also make mistakes sometimes, they do not perform the above anti-consumer practices when it comes to rectifying their mistakes. In general one of the best reflection of a person or an organisation's integrity, is how they take responsibility for their own mistakes, and Evetech fails to do that in ways that other retail shops do not.