Is it permissible to allow employees to sleep during a night shift free of breakdowns, and is it permissible for me to do so, and what is the religious ruling if I were to allow them to do so?

If the authorized manager permits the division of shifts in such a way that everyone can rest and sleep without affecting work or causing shortcomings, then there is no harm in that. However, if the manager is not authorized, or if the matter is strictly mandated by the factory owners, or if sleeping would cause disruption in the factory and production, or if there is an added benefit to the work by everyone remaining awake, then it is not permissible to violate what has been agreed upon. This is because the employee is a "private wage-earner" whose services are due to the employer throughout official working hours, and he is not allowed to violate that or delegate someone else.