Ask questions that will get each party involved in discussing options and possibilities. Find out what it would take to make the problem go away for each of them, offer suggestions that will enable that to happen. Finally, follow up . Check back with all parties a few days and then again a few weeks after the incident. Be sure that everyone has followed through on what they were expected to do and that everything is satisfactory from each person's point of view.
Most difficult people fear change .
They rely on consistency and predictability and repetition for their security. If that security is threatened by new rules, new expectations, challenges for which they feel unprepared or inadequate, then they will react with hostility, turf protection and withdrawal. They feel their power is diminished and sometimes feel like everything they have worked for and invested their time to build is slipping away. Coworkers who fear change may appear surly, aggressive, snappish, belligerent, manipulative, rude, condescending, patronizing, moody, withdrawn, anxious or skeptical. They may develop health problems , such a high blood pressure or heart irregularities, or begin to overeat and gain weight.