Hershey's attempt to modernize its enterprise system through the 'Enterprise 21' project in 1999 faced severe issues that led to significant candy shortages during critical sales periods, particularly Halloween. The project experienced delays due to an aggressive timeline and poor execution of a direct cutover strategy, resulting in $100 million in lost sales and a decline in stock prices. Although Hershey eventually rebounded in 2000, the implementation flaws highlighted the importance of thorough testing, adequate training, and realistic project planning in ERP system transitions.