I had a customer place an order and enter their address. When it came time to fulfill the order and print the shipping label I printed it out like I normally do and sent the package on its way. Some days later I received a message from someone who had received the package by mistake. According to them the address on the shipping label did not even exist.
I opened a support case and was told that the shipping software will substitute a different address in place of the one the customer entered if it thinks the address in the software is more correct. In this case Shopify's software substituted an address which was not only incorrect, but did not even exist. Shopify's reply was to just check the labels and if the address is different, then use a different shipping service outside Shopify.
In the end I lost the cost of my shipping for the package that was returned undeliverable. Shopify support was useless. They told me that although it was 100% their mistake, there would be no refunds, no Shopify credit, no nothing at all. In fact they made me feel like I was lucky they were even talking to me. I felt this was very poor customer service by Shopify. Lesson learned. So a warning to others: Do not trust Shopify's buggy shipping labels. You may want to purchase shipping and print labels elsewhere. I am exploring options.