fly in the ointment, a—some small or trifling circumstance which spoils the enjoyment of smth.:
- There is only one fly in the ointment offered by commercial propagandists; they want your money.
hair in the butter, a—(U.S. sl.) said of a delicate situation or sensitive issue:
- Never mind the details—which neither the Governor’s office nor anyone else is willing to share just yet—this is a real hair in the butter.