<div *ngFor="let field of selectFields; let i = index">
  <div class="role-list">
    <div class="role-list-box">
      <span for="select-{{ i }}">{{ i + 1 }}:</span>
      <select multiple [(ngModel)]="EsclatedRoles[i]" class="form-control"
              name="optionvalue" #optionvalue="ngModel" (change)="onSelectionChange(i)">
        <option *ngFor="let f of roles" [value]="f.entityId">
          {{ f.name }}
        </option>
      </select>
    </div>    
  </div>
  <div class="role-container">
    <div *ngFor="let selectedRole of EsclatedRoles[i]; let j = index" class="selected-role-box">
      <p-multiSelect
        [placeholder]="'Department'"
        [options]="allFields"
        optionLabel="name" 
        name="multi"
        optionValue="id" 
        [(ngModel)]="userRoles[i][selectedRole].Department"
      ></p-multiSelect>
      <p-multiSelect 
        [placeholder]="'Division'"
        [options]="allFields"
        optionLabel="name" 
        optionValue="id" 
        name="multisec"
        [(ngModel)]="userRoles[i][selectedRole].Division"
      ></p-multiSelect>
    </div>
  </div>
</div>

//I have already initialized my object array as per the count
userRoles = new Array(this.count).fill(null).map(() => ({}));

onSelectionChange(index: number) {
  const selectedRoles = this.task.config.EsclatedRoles[index];
  let savedRole = JSON.parse(JSON.stringify(this.task.config.userRoles[index]));  // saving the roles to reassign
  userRoles[index] = {};
  
  if (selectedRoles) {
    selectedRoles.forEach(role => {
      if (!savedRole[role]) {
        userRoles[index][role] = { Department: [], Division: [] };
      } else {
        userRoles[index][role] = savedRole[role];
      }
    });
  }
}

I have two nested ngFor loops, and for each selection of EscalaedRoles(2d array) (which is a multiselect field) I am generating an object with selected Role as key, and inside my object I have two MultiselectFields (department and divison), when I select some options in either department and divison, and select a new EscalatedRole, the selected options inside both p-multiselect vanishes, although they are still present in the object, hence the 2 way binding is correct otherwise the data will not be there, I tried everything from change detection to changing the data structures of userRoles, still I am getting the same error.
help me out in this, and I wanna know eher I am making mistake, or if anyone have better alternative