textbooks are dead wrong about 直す

Actually, textbooks completely miss the point of 直す. They give you ten different meanings like 'to fix' or 'to translate' but it literally just means 'to make straight.' Think about it. When you fix a mistake, you straighten it. If you walk (歩く) back on track, you straighten the path. It has nothing to do with 'repairing' complex stuff. Honestly, just translate it as 'straighten' in your head and you'll never get it