Embedded view not showing when switching between views using ngIf - angular6

Question

My component A has a child component B. On start up, A shows up because of conditition in *ngIf. A uses an EmbeddedView show show image thumbnails. A also has a button which when clicked changes the condition of *ngIf and shows B (because B shows on some other condition of *ngIf). If a button in B is pressed then A shows back again.
A's html is something like
<div *ngIf="this.tabType == this.questionTab" id="form-div-question" class="body__div--background">
....
<ng-template #thumbnailTemplate let-context="context">
<div id="{{context.divId}}">
<button id="{{context.buttonId}}" type="button" data-toggle="modal" (click)="showEnlargeImage(context)">
<img id="{{context.imgId}}" src="{{context.imgSrc}}"/>
</button>
<a *ngIf="this.isEditing" href="javascript:void(0)" id="{{context.closeId}}" (click)="deleteThumbnailFromContainer(context)"></a>
</div>
</ng-template>
...
<div id="image-thumbnail-container">
<ng-container #thumbnailContainer ></ng-container>
</div>
</div>
<div *ngIf="this.tabType == this.submittedAnswerTab" id="form-div-submitted-answer" class="body__div--background">
<b-component #bComponent [someInput]="..." (someEventFromB)="switchToQuestionTab($event)"></b-component>
</div>
The EmbeddedView in A is access as follows
#ViewChild("thumbnailContainer",{read:ViewContainerRef})
thumbnailContainerRef:ViewContainerRef;
What I am noticing is that on start up A shows fine including its embedded view. Then B also shows when the button in A is clicked. But when the view switches back to A then the embedded view doesn't show up!! (rest of A shows up correctly). I tried to force recreating the embedded view, I get error that the reference to the container is not defined (i.e.thumbnailContainerRef is undefined).
I also notice that when B is shown, it seem to be initiated everytime but when A is shown, it is not reinitialised everytime (maybe because B is child and A is parent)
Why is the container reference becoming undefined?

Answer 1

Taking inspiration from Angular 2 Show and Hide an element and What is the difference between *ngIf and [hidden]?
I seem to have solved the problem by using [hidden] instead of ngIf of A component.
<div [hidden]= "this.tabType != this.questionTab" ...>
</div>
<div *ngIf="this.tabType == this.submittedAnswerTab" id="form-div-submitted-answer" class="body__div--background">
<b-component #bComponent [someInput]="..." (someEventFromB)="switchToQuestionTab($event)"></b-component>
</div>
It seems that when '*ngIf' is false for A, Angular removes the embedded view and it doesn't get created again which seem to to be the reason why the ViewContainerRef is undefined when I switch back to A. Using [hidden] just hides A. Maybe there is code smell in my implementation but hey, I am still learning!