The phrase "a key error" is correct and usable in written English.
It can be used in contexts related to programming, data analysis, or any situation where a significant mistake or issue is identified.
Example: "The program crashed due to a key error in the code that prevented it from executing properly."
Alternatives: "a critical mistake" or "a major error".
He diagnosed a key error in the way the argument had been framed.
The Indians, who again hurt themselves with a key error, have lost four of five.
A key error by the 10-time Gold Glove catcher Ivan Rodriguez helped the A.L. West-leading Mariners score three times in the eighth.
John Judis, in a perceptive New Republic piece, came close citing "her refusal to apologize for the 2002 war resolution" as a key error.
RANGERS 8, RED SOX 6: Alex Rodriguez hit his major league-leading 37th homer, and Ivan Rodriguez made up for a key error by scoring the go-ahead run as host Texas rallied past Boston.
It was a key error by the linesman, but it gave Liverpool something to rail against in the second half and they began with a sense of injustice, desperately attempting to cancel out Stoke's lead.
That, in turn, introduces a slight but key error into temperature calculations.
Former South Carolina Attorney General Charlie Condon, who attended the hearing in support of Wilson, told HuffPost that he thinks Manning made a "key factual error".
But it was Kahn who made the key error that allowed Ronaldo to score the first goal and deflate the pretensions of a German team that was rarely more than workmanlike.
Another key error identified by the Columbia report was that Erdely had never spoken with the alleged perpetrators of the rape, including the man Jackie said brought her to the fraternity event in September 2012, named in the story as "Drew".
One key error he notes was underestimating how long children and adults should stay home because they remained infectious after their fever disappeared -- much longer, it turns out, than the 24 hours recommended by health officials.
