Duplicate Resource/Data added in FHIR Repository

Probably the best way to avoid these duplicate POSTs is to use conditional update. 

The conditional update interaction allows a client to update an existing resource based on some identification criteria, rather than by logical id. To accomplish this, the client issues a PUT as shown:

  PUT [base]/[type]?[search parameters]

When the server processes this update, it performs a search using its standard search facilities for the resource type, with the goal of resolving a single logical id for this request. The action it takes depends on how many matches are found:

• No matches, no id provided: The server creates the resource.
• No matches, id provided: The server treats the interaction as an Update as Create interaction (or rejects it, if it does not support Update as Create)
• One Match, no resource id provided OR (resource id provided and it matches the found resource): The server performs the update against the matching resource
• One Match, resource id provided but does not match resource found: The server returns a 400 Bad Request error indicating the client id specification was a problem preferably with an OperationOutcome
• Multiple matches: The server returns a 412 Precondition Failed error indicating the client's criteria were not selective enough preferably with an OperationOutcome

You can read about this operation type here: https://www.hl7.org/fhir/http.html#update