I only have a problem about once every 150 sales. About 90% of problems come from people who aren't familiar with ebay, don't read the rules, or are in the habit of automatically blaming somebody else when they screw up.
When there is a really late item, it could be the person is elderly and may have been suddenly hospitalized and unable to mail the item.
I always give them a break, hoping that if I ever fail, someone will at least give me the benefit of the doubt. In return, I get the other 149 sales as great service.
Also, if I run across someone who says they are selling something like an heirloom quilt to help pay for their daughter's hospitalization, I put that person on my prayer list.
It makes all the difference in how I feel about others in the marketplace.
Ebay is a great source. I'm sure there are others, but I've had very, very good luck over the last several years with them.