deselecting checkbox is removing whole row from the array mapped angular 4

i have this Panel array coming from backend which has another array Tests. i have mapped them on my custom accordion with checkboxes. the problem i am facing is i should be able to select/deselect Tests without removing it from the from front-end like it Disappears when i deselect. how can i solve this issue?

you can see from that image

https://i.stack.imgur.com/qJUFy.png

**here is my html file**

<ngb-panel *ngFor="let panel of panels" id="" [title]="panel.Name">
<label class="custom-control custom-checkbox">
    <input type="checkbox" class="custom-control-input" [name]="panel.Id + '-' + panel.Moniker" [ngModel]="checkAllTestsSelected(panel)"
      (ngModelChange)="onPanelCheckboxUpdate($event, panel)" [id]="panel.Id + '-' + panel.Moniker">
    <span class="custom-control-indicator"></span>
  </label>

 </ng-template>
 <ng-template ngbPanelContent>
<div class="individual-panel" *ngFor="let test of panel.Tests">
  <span class="text-dimmed"></span>
  <span *ngIf="panel.Name.includes('ENA') || panel.Name.includes('Celiac')">
  <label class="custom-control custom-checkbox">
    <input type="checkbox" class="custom-control-input" [name]="test.Id + '-' + test.Code"
           [ngModel]="testSelectionSession.SelectedPanelIds.indexOf(panel.Id) > -1 || testSelectionSession.SelectedPanelIds.indexOf(test.AssociatedPanel?.Id) > -1"
           (ngModelChange)="onTestCheckboxUpdate($event, test, panel)" [id]="test.Id + '-' + test.Code">
    <span class="custom-control-indicator"></span>
  </label>
  </span>
</div>

ts file

checkAllTestsSelected(panel: TestOrderPanel) {
  // get all individual test panels
  let individualTestPanelIds = panel.Tests.reduce((acc, test) => {
   if (test.AssociatedPanel) {
    acc.push(test.AssociatedPanel.Id);
  }
  return acc;
}, []);

// check if all individual test panels are selected
let allIndividualTestsSelected = individualTestPanelIds.reduce(
  (acc: boolean, panelId: number) =>
    acc && this.panelIds.indexOf(panelId) > -1,
  individualTestPanelIds.length > 0 &&
  panel.Tests.length === individualTestPanelIds.length
);

// if selected, remove all individual test panels and add the panel group
if (panel.Tests.length > 0 && allIndividualTestsSelected) {
  this.panelIds = this.panelIds.filter(
    panelId => individualTestPanelIds.indexOf(panelId) === -1
  );
  this.selectedPanels = this.selectedPanels.filter(
    selectedPanel => individualTestPanelIds.indexOf(selectedPanel.Id) === -1
  );
  this.panelIds.push(panel.Id);
  this.selectedPanels.push(panel);
  this.updateSession();
 }
  return this.panelIds.indexOf(panel.Id) > -1;
  }


 onPanelCheckboxUpdate($event: boolean, panel: TestOrderPanel) {
   let testPanelIds = panel.Tests.reduce((acc, test) => {
    if (test.AssociatedPanel) {
    acc.push(test.AssociatedPanel.Id);
  }

  return acc;
}, []);
// Wipe any duplicates
this.panelIds = this.panelIds.filter(
  panelId => panel.Id !== panelId && testPanelIds.indexOf(panelId) === -1
);
this.selectedPanels = this.selectedPanels.filter(
  selectedPanel =>
    panel.Id !== selectedPanel.Id &&
    testPanelIds.indexOf(selectedPanel.Id) === -1
);

if ($event) {
  this.panelIds.push(panel.Id);
  this.selectedPanels.push(panel);
   }
   this.updateSession();
 }

 onTestCheckboxUpdate($event: boolean,
                   test: TestOrderPanelTest,
                   panel: TestOrderPanel,
                   index) {

let testPanelIds = panel.Tests.reduce((acc, test) => {
  if (test.AssociatedPanel) {
    acc.push(test.AssociatedPanel.Id);
  }

  return acc;
}, []);
let associatedTestPanels = this.testSelectionSession.IndividualTestPanelsForAll.filter(
  testPanel => testPanelIds.indexOf(testPanel.Id) > -1
);
// If the panel is selected and a test within the panel is deselected,
// remove the panel and back all of the individual tests
if (this.panelIds.indexOf(panel.Id) > -1 && !$event) {
  this.selectedPanels = this.selectedPanels.filter(
    e => e.Tests.splice(index, 1)
  );
}

let clickedTestPanel = associatedTestPanels.find(
  testPanel => (test.AssociatedPanel ? test.AssociatedPanel.Id : -1) === testPanel.Id
);

if (clickedTestPanel) {
  // Wipe any duplicates
  this.panelIds = this.panelIds.filter(
    panelId => clickedTestPanel.Id !== panelId
  );
  this.selectedPanels = this.selectedPanels.filter(
    panel => clickedTestPanel.Id !== panel.Id
  );

  // Add individual panel if checkbox selected
  if ($event) {
    this.panelIds = this.panelIds.concat(clickedTestPanel.Id);
    this.selectedPanels = this.selectedPanels.concat(clickedTestPanel);
  }
}
  this.updateSession();
}

this.panelIds includes IDs of panels and this.selectedPanels includes whole panel array which is selected.

i have created a stackblitz too

stackblitz

can someone help? Thanks