The failings of friends, colleagues, and partners can be deeply galling. We got close to them because of their skills and merits. But, over time, those can be the disappointing side of their personalities that can ruin our view of them.
This leads us to the Weakness of Strength Theory. This dictates that we should see the weaknesses of people as the inevitable downside of the merits that initially drew us to them. From which we drew benefits at other points. We are not seeing their FAULTS, we are seeing the shadow side of the things that are genuinely good about them. We are picking up on weaknesses that derive from strengths.
Every strength that an individual has, brings a necessary weakness. It is impossible strength or virtue has a shadow weakness.