bullmq: Bug? - Error in processor permanently breaks entire queue

Consider the following setup:

// Queuer
import { Queue } from 'bullmq'


const queue = new Queue('mailer'),
      mails = [
        {
          from: "manast@taskforce.sh",
          subject: "This is a simple test",
          text: "An email sent using BullMQ",
          to: 'user@localhost',
          attachments: [{ filename: 'test.txt', content: Buffer.from('hello world!', 'utf-8') }]
        },
        {
          from: "manast@taskforce.sh",
          subject: "This is a simple test",
          text: "An email sent using BullMQ",
          to: 'user@localhost',
          attachments: []
        },
        {
          from: "manast@taskforce.sh",
          subject: "This is a simple test",
          text: "An email sent using BullMQ",
          to: 'user@localhost',
          attachments: []
        },
        {
          from: "manast@taskforce.sh",
          subject: "This is a simple test",
          text: "An email sent using BullMQ",
          to: 'user@localhost',
          attachments: []
        }
      ]


;(async () => {
  for (let mail of mails) {
    await queue.add('mails', mail, {
      attempts: 0,
      backoff: {
        type: 'exponential',
        delay: 1000
      }
    })
  }
})

// Logger
import { QueueEvents } from 'bullmq'


const queueEvents = new QueueEvents('mailer')

queueEvents.on('failed', async ({ jobId, failedReason }) => {
  console.log(`Job ${jobId} permanantly failed, because: ${failedReason}`)
})

// Processor
import nodemailer from 'nodemailer'
import { Job } from 'bullmq'


const transporter = nodemailer.createTransport({ sendmail: true, newline: 'unix' })

export default async (job: Job) => {
  const response = await transporter.sendMail(job.data)
  console.log(job.id, response.messageId)
}

When running this, the queue breaks when the first erroneous mail is processed. The “logger” will console.log something like Failed job 9880, because: The "chunk" argument must be of type string or an instance of Buffer or Uint8Array. Received an instance of Object, which is correct and expected, but all subsequent jobs will fail, too. Even though they are correct and Nodemailer doesn’t throw an error here.

Am I missing something?