Edit value for a key in a Map in Angular

Question

I have a model that uses a Map for eg: (I also have other properties such as Name)

export class User {
    _id!: string;
    accounts!: Map<String,Number>;
}

My mongoose model is:

var User = mongoose.model('user', {
    accounts : {
        type: Map,
        of: Number
    }
},'user');

I'd like to make editable for the frontend user

<div>
      <label>Accounts :</label>
      <div *ngFor="let account of userService.selectedUser.accounts | keyvalue">
        <label>Name: {{account.key}}</label>
        <input type="number" name="accountValue" #name="ngModel" [ngModel]="account.value" (ngModelChange)="account.value = $event" required>
      </div>
</div>

The key-value pairs show up in the browser but after submitting, all other properties get updated in MongoDB except for the map.