Got "mkdir(): File exists" message after multiple upload files via Dropzone, tried Storage::exists() doesn't work

I am creating a media library by using laravel and dropzone. When drag a folder to browser, it will send multiple requests to server.

But the second request always throws "mkdir(): File exists" exception. (No problem for the first request and after the second request)

For example:

Request 1:
fullPath: test folder/1.jpg
folder_id: 1
file: (binary)

Request 2:
fullPath: test folder/2.jpg
folder_id: 1
file: (binary)

Request 3:
fullPath: test folder/3.jpg
folder_id: 1
file: (binary)

Request 4:
fullPath: test folder/4.jpg
folder_id: 1
file: (binary)

Server saved the files for Request 1, 3, 4. And lost the file for Request 2.

I tried to check the folder is it exists by using Storage::exists() and delay between the each requests in Dropzone, but all doesn't work.

My code here:

    // MediaController.php
    public function upload(Request $request){

        $input_data = $request->all();

        $file = $input_data['file'];

        Media::saveMedia($input_data, $file)

    }

    // Media.php
    public static function saveMedia($data, $file){

        $media = new Media;

        $media->folder_id = isset($data['folder_id']) ? $data['folder_id'] : 0;

        $media->file_name = $file->getClientOriginalName();

        $mediaFolder = MediaFolder::create($media->folder_id, $folder_path); // $folder_path is "test folder"

        $media->folder_id = $mediaFolder->id;

        $media->save();

        // ...
    }

    // MediaFolder.php
    public static function create($parent_folder_id = 0, $folder_name){

        $is_exists_folder = MediaFolder::where(['parent_id' => $parent_folder_id, 'name' => $folder_name])->first();

        if(!$is_exists_folder){ // <-- expected false on Request 2 because Request 1 should be already saved to database, but actually true

            $parentFolder = MediaFolder::find($parent_folder_id);

            if(!$parentFolder){
                $parentFolder = new MediaFolder;
                $parentFolder->id = 0;
            }

            $new_folder_path = $parentFolder->getPath() . '/' . $folder_name;

            if(!Storage::exists($new_folder_path)){
                Storage::makeDirectory($new_folder_path); // <-- throws "mkdir(): File exists" exception on Request 2
            }

            $mediaFolder = new MediaFolder;
            $mediaFolder->name = $folder_name;
            $mediaFolder->parent_id = $parent_folder_id;
            $mediaFolder->save();

        }else{

            $mediaFolder = $is_exists_folder;

        }

        return $mediaFolder;

    }

via Chebli Mohamed