Below is the code snippet I am using to bind an ng-select present in a formgroup.

HTML:

<p>Select multiple elements using paste</p>
 <div class="col-md-offset-2 col-md-4">  
             <select style="widht:300px;" [ngModel]="selectedSearchFilter" (ngModelChange)="onChange($event)" name="sel3">
              <option [ngValue]="i" *ngFor="let i of searchFilters">{{i.name}}</option>
            </select>
        </div>  
<br>

<form class="form-horizontal" [formGroup]="personalForm" (ngSubmit)="onSubmit()">
<div style="background-color: gainsboro">  
   <div formArrayName="other" *ngFor="let other of personalForm.get('other').controls; let i = index" class="form-group">  
        <div [formGroupName]="i">  
              <div class="form-group" class="row cols-md-12">  
                <ng-select #ngSelect formControlName="searchCreteria"
                    [items]="people"
                    [multiple]="true"
                    bindLabel="name"
                    [closeOnSelect]="false"
                    [clearSearchOnAdd]="true"
                     bindValue="id"
                    (paste)="onPaste($event,i)"
                    (clear)="resetSearchCreteria(item)"
                    [selectOnTab]="true"
                    [closeOnSelect]="true">
                    <ng-template ng-option-tmp let-item="item" let-item$="item$" let-index="index">
                        <input id="item-{{index}}" type="checkbox"/> {{item.name | uppercase}}
                    </ng-template>
                </ng-select>
              </div>
        </div>  
    </div>  
</div>  
<button class="btn btn-primary" type="button"
       (click)="onClearDataClick()">Clear Data</button>
  </form>
  {{selectedSearchFilter | json}}

.ts:

import { Component, OnInit,ViewChildren,ElementRef } from '@angular/core';
import { DataService, Person } from '../data.service';
import { map } from 'rxjs/operators';
import { FormGroup, FormArray , FormControl, FormBuilder,Validators } from '@angular/forms';

@Component({
selector: 'multi-checkbox-example',
templateUrl: './multi-checkbox-example.component.html',

})
export class MultiCheckboxExampleComponent implements OnInit {

people: Person[] = [];
selectedPeople = [];

ngSelectCount=[];
personalForm:FormGroup;

searchFilters = [
   { name: "--Please Select Item", id: -1 },
{ name: "Country", id: 1 },
{ name: "States", id: 2 },
{ name: "Cities", id: 3 }];
selectedSearchFilter = this.searchFilters[0];
constructor(private dataService: DataService,private formBuilder: FormBuilder) {

}

 ngOnInit() {
  this.personalForm = this.formBuilder.group({
      filter: new FormControl(null),
      other: this.formBuilder.array([])  
    });
 }

  addOtherSkillFormGroup(filterName:string): FormGroup { 

      this.dataService.getRecords(filterName)
        //.pipe(map(x => x.filter(y => !y.disabled)))
        .subscribe((res) => {
            this.people = res;
            
            //this.selectedPeople = [this.people[0].id, this.people[1].id];
        });

   return this.formBuilder.group({  
    searchCreteria: [''] 
   });  
  }  

  onPaste(event: ClipboardEvent,i:any) {
  let clipboardData = event.clipboardData;
  let pastedData = clipboardData.getData('text');
    // split using spaces
    //var queries = pastedData.split(/\s/);
    var queries = pastedData.split(/\r\n|\r|\n/);
    //console.log(queries);
    // iterate over each part and add to the selectedItems
    queries.forEach(q => {
     var cnt = this.people.find(i => i.name.toLowerCase() === q.toLowerCase());
      console.log(cnt);
     if(cnt != undefined)
     {
        const control = <FormArray>this.personalForm.controls.other;
        const controlData = control.get([i]);
        controlData.get('isPointChecked').setValue(true);
        this.people[i]['isPointChecked'] = true;
    }});
   }
   onClearDataClick() {
    this.personalForm.reset();
  }
 onChange(e)
 {
  if(e.id != -1)
  {
   var cnt = this.ngSelectCount.find(i => i === e.id);
     if(cnt == undefined)
     {
       console.log(e.id);
      (<FormArray>this.personalForm.get('other')).push(this.addOtherSkillFormGroup(e.name));  
        this.ngSelectCount.push(e.id);
        this.selectedSearchFilter = e;
     }
  }
  else
  {
    this.personalForm.reset();
    this.ngSelectCount.length = 0;
   }
}

resetSearchCreteria(e)
{
  const index: number = this.ngSelectCount.indexOf(e);
  if (index !== -1) {
    this.ngSelectCount.splice(index, 1);
  } 
}
/////////////////////////////

}

data.service.ts:

import { Injectable } from '@angular/core';
import { Observable, of } from 'rxjs';
import { delay, map } from 'rxjs/operators';
import { HttpClient } from '@angular/common/http';

export interface Person {
id: any;
name: string;
}

@Injectable({
providedIn: 'root'
})
export class DataService {
constructor(private http: HttpClient) { }
getRecords(term: string = null): Observable<Person[]> {
    let items = this.getData(term);
    return of(items).pipe(delay(200));
}

getData(filterType: string) {
if (filterType == "Country") {
  return [
    { id: 1, name: "India" },
    { id: 2, name: "Switzerland" },
    { id: 3, name: "Norway" },
    { id: 4, name: "Macao" },
    { id: 5, name: "Qatar" },
    { id: 6, name: "Ireland" },
    { id: 7, name: "United States" },
    { id: 15, name: "United Kingdom" },
    { id: 21, name: "United Arab Emirates" }
  ];
} else if (filterType == "States") {
  return [
    { id: 1, name: "State 1" },
    { id: 2, name: "State 2" },
    { id: 3, name: "State 3" },
    { id: 4, name: "State 4" },
    { id: 5, name: "State 5" },
    { id: 6, name: "State 6" },
    { id: 7, name: "State 7" },
    { id: 15, name: "State 8" },
    { id: 21, name: "State 9" }
  ];
} else {
  return [
    { id: 1, name: "City 1" },
    { id: 2, name: "City 2" },
    { id: 3, name: "City 3" },
    { id: 4, name: "City 4" },
    { id: 5, name: "City 5" },
    { id: 6, name: "City 6" },
    { id: 7, name: "City 7" },
    { id: 15, name: "City 8" },
    { id: 21, name: "City 9" }
  ];
  }
}
}

In the above code, I am attempting to bind different items based on dropdown selection. If the user selects "Country," then countries will be bound with ng-select, and if states are selected, then states will be bound. However, in my case, the last selection is reflecting for all form controls.

You can find a complete working sample here

Can you please assist me in configuring this case?