It may be just finding something that he likes..... some coats restrict how they move... the leg holes just aren't made right. I have found this with several things that I have purchased. Maybe something without leg holes? (they do exist.... I have some that have a collar and go around the neck and are belted at the waist.... kinda like a horse-blanket..... (sorry if your not familiar, but that is the best way I can think of to describe it
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Good Luck!