I returned a horse a few years ago because she cribbed. However, I called the former owner within a few days, not a few months. I was sold the horse as sound, but cribbing is an unsoundness. The deal was that I would have the coggins done and if it were positive or if the horse was unsound, that was a reason for undoing the sale. I should have looked at her teeth but neglected to this one time. I never would have taken the horse if I had seen the condition of her teeth.
IMO, if they called within a week, that is one thing, a few months, then "no".