Being a good specialist is, unfortunately, not the same as being able to lead other specialists. Managers should decide on promotions based on the leadership skills of their subordinates, not only on good performance.
5. You can't admit your own mistakes
Whether they like it or not, every manager is a role model for their subordinates. They should be able to admit their own mistakes and learn from them. Their staff will be inspired by such an act of leadership.
-Kk-