flaw

The jeweler used a magnifying glass to spot a tiny flaw inside the diamond.

(Chinese) 珠宝商用放大镜发现钻石内部有一个极小的瑕疵。

Lawyers discovered a fundamental flaw in the contract that made it legally void.

(Chinese) 律师们发现合同中有一个根本性的缺陷，导致其在法律上无效。