High turnover that is internal to an organization can be for natural reasons, unknown causes or because there is something seriously wrong with a department. High internal turnover is not an automatic indicator of anything that is wrong with the department or departments. There may be perfectly reasonable explanations.
But turnover is a problem in general. Once an employee has gone through a costly period of job orientation and training, it becomes a waste of effort when the employee moves on, and a new hire must start the process all over again. If the department has an ongoing workload, it is not feasible to maintain production with a staff that is constantly in the process of coming in or moving on.
Natural reasons include the nature of the work. Some departments are too isolated or highly specialized. Unless an employee wants to work at that same job with limited advancement opportunities for their entire career, most folks will try to move on as quickly as possible. Other departments service the entire, huge corporation, and offer far too many contacts and insights into the departments that offer broader opportunities for learning, advancement, and career saving lateral moves.
Unknown causes are situations that need to be investigated. Something as simple as the nature of the work and the lack of attention or appreciation can make employees flee as soon as they get there. The department's physical distance from the other parts of the company can give creepy feelings of being banished to a place of low regard, out of the excitement, and under some kind of punishment. There is little opportunity to develop feelings of belonging to the corporation as a whole, and to developing loyalty.
In actuality, there are some people who prefer to be isolated from the masses, who love the work, and who have a great time working at a distance from the corporate or company center. Whatever the cause, investigation cannot stop until the root cause of the turnover is discovered and the situation corrected.
In some cases, managers from other departments develop recruitment schemes where one department constantly gets "raided". Often this is because that department has a reputation for conducting the best company orientation and on the job training! What a reward it is to be raided!
Something seriously going wrong can range from bad, bad management to criminal activity. A department can develop a rogue atmosphere, usually resulting from a leadership vacuum where people leave before they get hurt or lose their jobs. In the absence of any other explanation, a detailed look at the day to day activities of both management and the employees may have to involve company security, assigning a person to observe the floor activities, and detailed review of personnel changes, formal complaints, and other actions.
The leadership quality needs to be evaluated, also. In some cases, the top manager cannot even produce reports or answer questions when given the most ample deadlines in which to do so. That should indicate that the manager is not capable doing much about what is going on in his or her out of control department.
Other indicators of a leadership vacuum are budgets for overtime that are off the charts for extended periods. When union grievances, incidents, accidents, excessive sick and other leave, formal complaints, EEOC complaints, and other indicators of substandard department health are off the charts, that is a sure sign that someone at the top has not been doing their job for a while.
So, as the internal cases of high turnover can widely vary, and have widely varied causes, the sooner the situations are cleared up, the sooner the department that is suffering the turnover can get back to doing the work that it is set up to do.