Having to rewrite a pattern to do it a simpler way.
The number one complaint is running out of bobbin thread. Not a problem with a drop in bobbin. I always know when my bobbin is running out because I can see it.
Running out of a fabric that you can no longer find. They discontinue fabrics so fast. Also shops that dont carry a complete line of a fabric line. Especially the basic fabric that holds the line togather.