dropdown hidden behind modal and unclickable with nz-zorro

couple days ago i update my app to angular 9, and now i sometimes see broken elements. i am using ng-zorro\angular material.

i get problem when nz-select drop-down disapear behind screen.

html:

         <div>
            <nz-select  [(ngModel)]="exampleSelectedValue">
                <nz-option
                    nzLabel="{{item.description || 'Example ' + (i+1)}}" nzValue="{{i}}" *ngFor="let item of data.metadata.examples; let i= index"></nz-option>
            </nz-select>
        </div>