Mongoose and GridFS : File upload fails (TypeError: Cannot read properties of undefined (reading '_id'))

Question

I'am working on a nodejs project that uses gridfs with mongoose. I'm currently trying to upload a file to GridFS but i always have the same error:

TypeError: Cannot read properties of undefined (reading '_id')
    at GridFSBucketWriteStream.emitFile (C:\Users\user\app\node_modules\multer-gridfs-storage\src\gridfs.ts:353:12)
    at GridFSBucketWriteStream.emit (node:events:530:35)
    at GridFSBucketWriteStream.emit (node:domain:488:12)
    at finish (node:internal/streams/writable:945:10)
    at processTicksAndRejections (node:internal/process/task_queues:82:21)
[nodemon] app crashed - waiting for file changes before starting...

I have followed many tutorials (and github issues) but none of them worked for me.

Connection init.

async function initMongodb() {
  mongoose.connect(env.MONGODB_HOSTNAME);

  mongoose.connection.once("open", () => {
    logger.docs("MongoDB database connection established successfully");
  });

  let bucket;
  mongoose.connection.on("connected", () => {
    logger.info("MongoDB connected for GridFSBucket")
    bucket = new mongoose.mongo.GridFSBucket(mongoose.connection.db, {
      bucketName: "files",
    });
  });
}

The function that create an storage engine from GridFs

import { GridFsStorage } from "multer-gridfs-storage";
import multer from "multer"
import { env } from "../config/env";

// Create storage engine
export async function upload() {
    const mongodbUrl = env.MONGODB_HOSTNAME;

    const storage = new GridFsStorage({
        url: env.MONGODB_HOSTNAME,
        file: (req, file) => {
            return new Promise((resolve, reject) => {
                const fileInfo = {
                    filename: "POPO",
                    bucketName: 'uploads',
                    mode: "w",
                    options: {
                        w: "majority"
                    }
                };
                resolve(fileInfo);
            });
        }
    });

    return multer({ storage });
}

How i'm calling it:

.... (await upload()).array('attachments'), .....

I have lost hope :(