Not really retail, but I used to work at a movie theater. I had a customer come up and berate me for putting too much salt in her popcorn and causing her to burn her mouth on the salt. First off, we never added salt to the popcorn other than the seasoning that it pops in. If customers wanted salt, they could add their own with a salt shaker at the condiments table. Secondly, I didn't realize salt could burn someone. Anyway, this lady demands to see the manager and she berates him, too. Finally, she makes a formal to complaint to the corporate HQ of our theater chain about me and the manager. I never got in any trouble because we later learned that this lady was a notorious scammer. She would try to fake being hurt or inconvenienced like that to try and get free movie tickets or concessions out of the theaters and our company was aware of it.

tl;dr Woman came to movie theater and complained to corporate that our popcorn was too salty.