I recently ordered some coffee from Square Mile Roasters - had never tried them before but had heard good things. I know coffee is a really subjective thing, but one bag I just didn't get on with, however I tried making it - it just had zero taste to it.
I'd also seen someone else I know complaining about it. I contacted customer support to let them know, in case it was a bad batch - with no expectations from me as to anything in return.
Their customer support was really good - they not only sent me out a different coffee (which was amazing) but took the time to talk through my current brewing process, and put me in touch with one of their brewers, who gave me personalised advice on my coffee-making process. As a result, my coffee brewing process now feels 100 times better, and I feel really good about the brand and must have told half a dozen people about the experience, and am already planning what I order next.
A small and some might say a minor story, but it highlights an important point. Don't just design for the happy path for your customers. Think about what you do when things go wrong, you can turn average customer experiences into good ones, and build brand loyalty in the process.