2 questions: Bits && bucking...?

I don't really have much experience with riding in bits, but the horses that i do ride, if at a point any of them buck it generally mean that their back is sore. it wouldn't hurt to get her checked out anyway, so that when it happens again if you get her treated you know that she is Just being and she's not sore. If she doesn't like the bit, it could be that reason, but there's no harm getting her back checked anyways.