What about a mother's anger towards her son when he has not erred?

It is not permissible to displease one's mother, for the pleasure of Allah Almighty lies in the pleasure of the parents, and His displeasure lies in their displeasure. The son must satisfy his parents, and it is forbidden to displease them. Their satisfaction takes precedence unless they command disobedience or the abandonment of an obligation. If the mother is angry, even if the son did not commit a direct mistake, her anger might be due to his shortcomings in showing her dutifulness, which is considered a negative form of disobedience.