Chink refers to a narrow opening. It’s often used in the phrase chink in [one's] armor, which refers to a weakness that provides an opening for attack. Another common use is in the phrase chink of light (or sunlight), which appears most often in British writing and is similar in meaning to ray of hope. Kink has a few meanings, including (1) a tight curl in rope or wire, (2) a painful muscle spasm, (3) a flaw in a plan, and (4) an unusual sexual taste or behavior. None of its meanings have to do with small openings so kink in [one's] armor makes no logical sense.
The use of chink as a slang term for any group of people is offensive.
There are a few ways in which kink and chink are sometimes confused. The most common is the use of kink in place of chink in the phrase chink in [one's] armor—for example:
Volstad has pitched well in Turner Field in the past with the only kink in the armor being giving up the long ball. [Fish Stripes]
And that is the kink in the CBR’s otherwise impenetrable armor. [Motorcycle USA]
These are positive examples:
Such hype was anathema for the modest professional fighter, who has 22 victories under his belt, and not a perceptible chink in his armour. [Telegraph]
The lack of snow put a slight kink in the Snowy Range Ski Area’s plans for opening. [KOWB]
But a chipmunk doesn’t feel secure until it’s in its burrow or has found a chink somewhere to hide in. [Washington Post]
The Blues had done a great deal of work this season to iron out their performance kinks. [New Zealand Herald]