Angular Material Table With Expandable Rows, Automaticly Expanded When Change Tabs With StackBlitz Example

I have an Angular material table with expandable rows. In every row, I have multiple tabs, On the first tab, I have another table with expandable rows. At the start al the rows are

Solution 1:

I found my answer. Apparentely I have to add <ng-template matTabContent></ng-template> to the <mat-tab>