MVC loading from stream

[IvanSammut]

I have a frame on an mvc view which I want to load the contents from a stream I am getting thru an Action.

The Action code is this

[HttpGet]
public ActionResult DownloadShipmentLabel2(Int64 fileID, bool inline = false)
{
clsConsignmentFilesHelper myHelper = null;
string sErrorMessage = null, sFileName = null;
try
{
sFileName = clsDBFunctions.GetFieldFromKey("CR_Consignment_Files", "ID", fileID, "FileName", ConnectionString.GetConnectionString(clsDefaults.eCompanyFunctionality.FedEx)).ToString();
if (!string.IsNullOrWhiteSpace(sFileName))
{
string mimeType = System.Web.MimeMapping.GetMimeMapping(sFileName);
myHelper = new clsConsignmentFilesHelper(ConnectionString.GetConnectionString(clsDefaults.eCompanyFunctionality.FedEx));
byte[] buffer = myHelper.DownloadConsignmentFileToBytes(fileID, "FedEx", out sErrorMessage);
if (buffer != null)
{
MemoryStream stream = new MemoryStream(buffer);
if (inline)
Response.AddHeader("Content-Disposition", $"inline; filename={sFileName}");
else
Response.AddHeader("Content-Disposition", $"attachment; filename={sFileName}");

                    return File(stream, mimeType);
                }
                else
                {
                    return new HttpStatusCodeResult(500, sErrorMessage);
                }
            }
            else
            {
                throw new Exception($"Could not retrieve the file name for the specified shipment labels ({fileID}).");
            }
        }
        catch (Exception ex)
        {
            clsDBFunctions.HandleError(ex, $"_downloadShipmentLabel({fileID})", "FedExController");
            return new HttpStatusCodeResult( 500, ex.Message);
        }
        finally
        {
            if (myHelper != null) myHelper = null;
        }
    } 

Then I have the following script to fill the frame with the pdf contents

function printConsignmentFile(fileID) {
const iframe = document.getElementById('viewer');

const pdfUrl =
    '/fedex/DownloadShipmentLabel2?fileID=' + fileID + '&inline=true';

iframe.src =
    '/pdfjs/web/viewer.html?file=' + pdfUrl + '&autoprint=1';

}

but I keep getting the following error in fetch_stream.js function fetchUrl

GET http://localhost:30114/fedex/DownloadShipmentLabel2%3FfileID%3D1316333 400 (Bad Request).

The url is fine cause when it is not inline the file is downloaded.

Can someone please help?
Thanks
Ivan