File received via Web API is not opening

I can upload the documents from external application to the Appian.

When try to open the received documents with file extensions .docx,.pdf,.pptx, the files are throwing error and after I select "Repair" option, then the files are opened.

But the files with extension .xlsx,.zip,.png,.bmp are not opening and its throwing "file format or file extension is not valid" error and unable to open the files.

Step 1: By using, "Document Upload" Web API can receive document from external application to Appian.

a!startProcess(
      processModel: cons!DSC_UPLOAD_CWR_DOCS,
      processParameters: {
        transcript: http!request.body,
        cwrId: http!request.queryParameters.cwrId,
        documentType:http!request.queryParameters.documentType,
      },
      onSuccess: a!httpResponse(
        statusCode: 200,
        headers: {},
        body: concat(
          "Upload Successful: ",
          document(http!request.body, "id"),
          " - ",
          document(http!request.body, "name"),
          ".",
          document(http!request.body, "extension")
        )
      ),

Step 2: Process Model which receives the document details and uploaded in the application

             Set Document Details: - Map the received document details to the CDT

           Move Document: - Move the received document to the custom folder. Document uploaded with its original size.

           Write Document: - Add document details to the database

                                            Able to see the document in the UI

I downloaded the documents from document folder and also directly from application. Got the below error when I tried to open the downloaded documents

When I select Ok/Yes from the error window, the files with extensions .docx,.pdf,.pptx are opened. But files with extensions .xlsx,.zip,.png,.bmp are not opened.

Any suggestions to fix this issue.