i once looked after a neighbours cat while they were holidaying. after id been a couple of times and knew the cat was ok, i was disturbed on the next visit, to see him kinda staggering when he walked, his tail kinked in the was you describe, basically 'wrong'. i called them in the middle of their holiday, cos i thought he had been in an accident. it turns out that they said he has sort of fits and goes a bit like that sometimes and that it would pass in a couple of hours and not to worry and sorry they forgot to tell me! im assuming that this is what their vet told them.