A developer is building a system to automatically categorize customer feedback. They want a large language model to label each piece of feedback with one of three specific labels: {positive, negative, neutral}. However, when they use the prompt below, the model often generates free-form answers like 'The customer is unhappy' or 'This is a bad review' instead of the required labels.

Prompt Used: Identify the sentiment of the following customer feedback. Input: The shipping was incredibly slow, and the item arrived damaged.

Analyze the developer's prompt. Explain the most likely reason why the model is not consistently returning one of the required labels and describe a specific modification to the prompt's instruction that would resolve this issue.