2011 고2 6월모의고사 25번 문제인데요...

원래 문장: only when the man was coming down and had reached the height of the eaves did the expert call out, be careful! watch your step coming down!

변형된 문장: only when the man was coming down and had reached the height of the eaves the expertcalled out
,be careful! watch your step coming down!여기서 이 변형된 문장이 문법적으로 맞는말인가요? 만약틀리다면 틀린 이유좀 설명해주시고, 맞는이유도 설명부탁드려요 ㅜ