My Teddy had a history of issues with the farrier when I got him, but he was OK the first couple of times when I held him. The third time, he snatched one of his hooves back, reared up, and got all kinds of upset. Eventually the farrier got him taken care of, but it took several tries. I noticed that it was only the one foot, and only when he was being rasped, not trimmed. I talked to a bunch of people, including here, and my instructor, and we came to the conclusion that there was something about that leg that was bothering him. Then I had a body worker out for all of them, and she discovered, basically, that there was an old injury that made it really painful for him to have his foot lifted up and out. Teddy just saw the farrier today, and I told him about it and asked him to just take it really slow and careful with that one leg. He did, and we didn't have any problems.
I'm posting all of this basically to say that if it's the same foot over and over again, there might be some sort of injury / pain issue. Of course, it could be any number of things, but I thought I'd throw that out there.