답변해주시는 선생님들 모두 수고많으시고 또 감사합니다.

every one of the toddlers crawled over to help him pick up the pins or books, but only in those instances where his facial and bodily gestures suggested he needed assistance.

문장에서 but뒤를 살펴보면
but only in those instances where his facial and bodily gestures suggested he needed assistance.

가 있는데요.. 여기서 where his facial and bodily gestures suggested he needed assistance는 앞에 있는
those instance를 수식해주는 관계부사입니다.

그럼 문장구조가
but only in those instances [where his facial and bodily gestures suggested he needed assistance].
가 되는데... but을 제외한 only in those instances는 명사구가 아닌데 but뒤에 올 수 있나요?

알려주세요 :)