Fly in the ointment (Ecclesiastes 10:1)

bible verse

“As dead flies give perfume a bad smell, so a little folly outweighs wisdom and honor.”

meaning

It is a small problem that upsets a plan or scheme, or stops something from being perfect.

origin and application

When there is a fly inside a bottle of perfume, it spoils or prevents complete enjoyment of its otherwise pleasant scent.

example

His jumpy career history turned out to be the fly in the ointment when he applied for a job.