chink in one's armor

1. A vulnerable area, as in Putting things off to the last minute is the chink in Pat's armor and is bound to get her in trouble one day. This term relies on chink in the sense of “a crack or gap,” a meaning dating from about 1400 and used figuratively since the mid-1600s.

Example Sentences

But he can understand why others use it in puzzles, since “a chink in one’s armor” is a common expression.

From Slate

The editor then used the word “chink” as an example, noting that it’s “benign in the sense as a chink in one’s armor.”

From Fox News