Angular forms not recognizing formControlName

I'm building a form which on the top contains filters. I'll show the functions that are called when the error ocurrs

public onChangeSubType(requestSubType: any) {
 const typeId = this.filterFormGroup.get('requestType').value.value;
 const subTypeId = this.filterFormGroup.get('requestSubType').value.value;
 const accountId = this.filterFormGroup.get('account').value;

 if (!subTypeId) return;

 this.detailList = [];
 this.setRequestModel(requestSubType.type);

 this.fieldSettings = Utils.manageFields(typeId, subTypeId);
 this.buildInvoiceForm();

 if (subTypeId === 77) {
  this.invoiceFormGroup.patchValue({ terminatedEmployees: true });
  this.fetchTerminatedEmployees(accountId);
 } else {
  this.invoiceFormGroup.patchValue({ terminatedEmployees: false });
  this.fetchEmployees(accountId);
 }

}


private buildInvoiceForm() {
    if (this.invoiceFormGroup) this.invoiceFormGroup.reset();
    const requestType = this.filterFormGroup.get('requestType').value.name;
    const requestSubType =
      this.filterFormGroup.get('requestSubType').value.name;
    const mainAccount = this.filterFormGroup.get('mainAccount').value.name;
    const account = this.filterFormGroup.get('account').value.name;
    const defaultSubject = `${requestType} - ${requestSubType} - ${mainAccount} - ${account}`;
    this.extraData = {
      employees: this.employees,
      categories: this.requestCategories,
    };
    if (this.fieldSettings) {
      this.invoiceFormGroup = new FormGroup({
        category: new FormControl('', [Validators.required]),
        subject: new FormControl(defaultSubject, [
          Validators.required,
          Validators.maxLength(200),
        ]),
        selectAll: new FormControl(false),
        employee: new FormControl(null, [Validators.required]),
        description: new FormControl('', [
          Validators.required,
          Validators.maxLength(200),
        ]),
        activityDate: new FormControl(''),
        attachmentFiles: new FormControl(''),
        terminatedEmployees: new FormControl(false),
      });
  }

invoice.html template

<div class="invoice-request__field flex-basis-30">
            <span class="lssai-label font-weight-bold"
              >{{
                this.invoiceFormGroup.get('terminatedEmployees')?.value
                  ? 'Terminated'
                  : ''
              }}
              Employees*</span
            >
            <ng-multiselect-dropdown
              formControlName="employee"
              [placeholder]="'Select Employee'"
              [settings]="accountMultiSelectSettings"
              [data]="employees"
            >
            </ng-multiselect-dropdown>
          </div>

onChangeSubType is called whenever the subType changes and I get the following error

ERROR Error: There is no FormControl instance attached to form control element with name: 'employee'

filterValueChanges() is called onInit()

private filterValueChanges() {
    this.filterFormGroup.valueChanges.subscribe((form) => {
      if (form.requestType === null) {
        this.requestSubTypes = null;
      }
      if (form.requestSubType) {
        this.onChangeSubType(form.requestSubType);
      }
      this.checkForCategoryNotApplyValues();
    });
  }

Just a final comment. If I change formControlName="employee" for [formControl]="invoiceFormGroup.controls['employee']" it works but gives me a tslint error.

How can I solve the error so I can keep formControlName="employee".