a fly in the ointmentinformalSPOIL the only thing that spoils something and prevents it from being successful 美中不足之处 The only fly in the ointment was Jacky. 唯一扫兴的人是雅基。
a fly in the ointment• There had to be a snag, of course, a fly in the ointment.
→ a fly in the ointment at fly2(3)