In real life, there is no isolated reason or solution to this kind of problem. Hence, in the course of one's career, the supervisor has to interact with individuals in his/her team and offer constructive advice to ward off any developing habits that could be detrimental to the individual or the team as a whole. Making sudden discoveries and abrupt terminal decisions, without considering the root causes, does not foster the correct working environment in an organization.
Therefore, in my opinion, supervisors should silently observe each individual, conduct root cause analyses of any unnatural behavior through discussions, provide sincere advice, and implement a time-bound improvement plan. Failing at any of these steps, terminal decisions should be made. Employees are the most valuable assets of any business, and mishandling such situations can leave a negative impact on other employees in the organization.