Angular Ng2-file-Upload Upload.all() not uploading file to API

Am trying to Upload Files mp4 and jpg extensions, I have 2 separate Fileuploader instance, with some custom validation imposed on 2 separate FileUploader, I have a upload button, onclick of the upload button am pushing Files in 2 FileUploader to a Single FileUploader and calling the inbuilt method upload all to upload the file to Server, but it's not hitting the server (API Service), I hereby paste the code below what I have tried please help me to resolve this issue.

File Uploader Initialization

    uploader: FileUploader;
    coverImageUploader: FileUploader;
    mergedFileUploader: FileUploader;
    options: FileUploaderOptions = {
        url: URL,
        authToken: `Bearer Token`,
        authTokenHeader: 'authorization',
        isHTML5: true,
        method: 'POST',
        itemAlias: 'file',
        headers: [{
            name: 'refId',
            value: ''
        }, {
            name: 'userId',
            value: ''
        }, {
            name: 'roleId',
            value: ''
        }]
    }

        this.uploader = new FileUploader(this.options);
        this.coverImageUploader = new FileUploader(this.options);
        this.mergedFileUploader = new FileUploader(this.options);
 

Pushing Files yet to be uploaded from 2 FileUploader to another FileUploader

      let files: any = []  
      files.push(this.uploader.getNotUploadedItems().filter((f: FileItem) => !f.isUploading))  
      files.push(this.coverImageUploader.getNotUploadedItems().filter((f: FileItem) => 
      !f.isUploading)) 

var merged = [].concat.apply([], files);
        merged.forEach(e => {
            e.options.headers.find((o, i) => {
                            if (o.name === 'refId') {
                    e.options.headers[i] = {
                        name: 'refId',
                        value: e.formData.reduce(r => r).RefId

                    };
                    return true;
                } else if (o.name === 'userId') {
                    e.options.headers[i] = {
                        name: 'userId',
                        value: user.userId.toString()
                    };
                    return true; 
                } else if (o.name === 'roleId') {
                    e.options.headers[i] = {
                        name: 'userId',
                        value: user.roleId.toString()
                    };
                    return true; 
                }
            })
        })
        this.uploader.clearQueue();
        this.coverImageUploader.clearQueue();
        this.mergedFileUploader.clearQueue()
        this.isUploadProcessing = true
        this.mergedFileUploader.addToQueue(files)

Upload Button Click Event Method

UploadFiles(){
this.mergedFileUploader.uploadAll()
}