矯角殺牛
Meanings
1
trying to fix a small flaw and ruining the whole thing
A yojijukugo (four-character idiom) used to warn against overcorrection that causes greater harm. Literally 'straightening the horns of a bull and killing it in the process'. Equivalent to 'the cure is worse than the disease'.
Trying to fix a small mistake and ruining the whole project is exactly a case of 'straightening the horns and killing the bull'.