[zhte415]

Use an external agency to give truly anonymous 360 degree feedback for everyone in the organisation.

This can get you get to the roots of problems. Take their advice on administering.

From what you stated, it sounds like the company is in a hierarchy power structure where others don't want to stick their head out too much.

At only 20 people, to have this problem sounds like a problem. Getting an external consultant to do some investigation seems to make sense.