Your salespeople must develop a belief system around a product, or it can't be sold. Before they can sell it, they must be sold on it themselves. Unfulfilled promises after the sale to the customer. Salespeople feel personally responsible for the promises they make. Negative attitude of the boss.
Grumpy boss equals low morale, equals high staff turnover.
Bosses create their own fate. Fights that no one wins. Production fighting sales. Accounting fighting sales. Outside people fighting inside people.