destructuring a mongoose document causes error

CompanyUser Schema

const companyUserSchema = new Schema({
  profile: {
    type: profileSchema,
    default: profileSchema
  }
})

profileSchema

const mongoose = require('mongoose')
const Schema = mongoose.Schema

const emergencySchema = require('./EmergencySchema')

function setFirstName (val) {
  if (val !== null) return val

  return this.first_name
}
function setLastName (val) {
  if (val !== null) return val

  return this.last_name
}

function dollarTrim (val){
  if (typeof val == "string" && val.trim().includes('$')) return val.trim().substring(1)
  return val
}

const profileSchema = new Schema({
  first_name: { type: String, trim: true, default: '', set: setFirstName },
  last_name: { type: String, trim: true, default: '', set: setLastName },
  supervisor: { type: String, trim: true },
  role: { type: String, trim: true },
  phone: { type: String, trim: true, default: '', set: val => val ? val.replace(/[\s()-]/gi,'') : ''},
  type: { type: String, enum: ['', 'hourly', 'salary', 'contractor'], default: ''},
  employee_type: { type: String, enum: ['', 'parttime', 'fulltime', 'contractor'], default: ''},
  pay_rate: { type: String, trim: true, set: dollarTrim },
  pay_day: { type: String, default: '' },
  pay_frequency: { type: String, default: '' },
  hours_per_week: { type: String, trim :true },
  start_date: { type: String, trim: true },
  address: { type: String, trim: true },
  address2: { type: String, trim: true },
  city: { type: String, trim: true },
  state: { type: String, trim: true },
  zip: { type: String, trim: true },
  state_work_in: { type: String, trim: true},
  dob: { type: Date, default: null },
  lastSocial: { type: String, default: '' },
  avatar_url: { type: String, default: '' },
  years_experience: { type: String, default: ''},
  contractor: { type: Boolean, default: false },
  _partner: { type: Schema.Types.ObjectId, ref: 'PartnerUser', default: null },
  conference: { type: String, default: ''},
  emergency_contact: {
    type: emergencySchema,
    default: {}
  },
  timezone: { type: String, default: '' }
}, {
  toJSON: { virtuals: true },
  toObject: { virtuals: true },
  _id: false,
  id: false
})

profileSchema.virtual('full_name')
  .get(function () {
    return (this.first_name + ' ' + this.last_name).trim()
  })
  .set(function (v) {
    this.first_name = v.substr(0, v.indexOf(' '))
    this.last_name = v.substr(v.indexOf(' ') + 1)
  })

module.exports = profileSchema

test that causes error

test.only('destructuring mongoose document', t => {
  const cu = new CompanyUser()
  const profile = {
    first_name: 'Tester',
    last_name: 'Testing',
    role: 'owner',
    phone: '818-497-4098',
    type: 'salary',
    employee_type: 'fulltime',
    pay_day: 'Friday',
    city: 'Test Town'
  }

  cu.profile = profile

  console.log({...cu})


  cu.profile = {
    ...cu.profile
  }
  console.log(1)
  console.log(cu) //crashes here with `obj.toObject is not a function`
  console.log(2) //does not occur
})