When an employee isn't working out, it's almost always because the role is a bad fit and not because they have deficiencies as an engineer or as a person. That

When an employee isn't working out, it's almost always because the role is a bad fit and not because they have deficiencies as an engineer or as a person. That's why performance improvement programs are so degrading and insulting. The person doesn't need to change, they need to be in a role that's better suited to their abilities, temperament, or whatever is causing the mismatch. Often that role is in a different company and if so then great because everyone is better off and that's a good thing.