Perhaps we need more information here so we understand what you are expecting from the output. An Aggregate snap works much like a database Group By… fields not listed in the “Group-By-Fields” property can have an aggregate function applied (sum, count, min, max, etc.) in the “Aggregate fields” table and would no longer be present in the output (except in aggregated form as specified).
Please review the Aggregate snap documentation to ensure this is the action you are looking for.
It almost sounds like you may really need either the “Group By N” or “Group By Fields” snap.
On the other hand, if you are trying to get aggregate values and keep the detail documents, you may need to use a Copy before the Aggregate, and Join the documents back after the Aggregate.