This may very well be related to OCD.
Many times, individuals with OCD fear not being perfect, so they look over things repeatedly, do far more research than is necessary, or do not turn things in because they are afraid of the consequences of not being perfect.
Your husband may believe that turning in something that is less than perfect is worse than not turning it in at all, possibly hoping his boss will just forget about the task.
However, as this behavior continues, your husband will become more and more fearful of not being perfect as he gets increasing pressure from his boss to actually complete his duties. Your husband could very possibly lose his job over this, and it is important for him to get some help so that he can start to be productive at work.
Many companies have an employee assistance program (EAP) that he can contact for free and that can help him find a therapist who could aid him in fixing this problem.