I am waiting for a shipment from him dating to 2007 ... I jest. However, having purchased from him many years past, he would, for example, either not ship to me all of the comic books that I had paid for or ship a fine copy of a book although I had purchased and paid for a VF/NM copy (if you grade that subjectively, you are in the wrong business). Of course, he would take several months to ship after I had paid him.
Thankfully, in the end, after many emails and voice messages (I don't recall that he ever answered his telephone), I was able to obtain a refund of all the money I had paid him for books he did not ship or shipped a lower grade copy of, although accepting my money for a higher grade copy. Strangely, I never received a higher graded copy than what I had purchased .