workaround-comment.ts

public dropped(event: CdkDragDrop<Item[], Item[], Item>) {
    // VirtualScrolling and CdkDropList don’t work well together.
    // Workaround solution: set the correct previousIndex manually.
    event.previousIndex = event.previousContainer.data.findIndex(
        (item) => item.id === event.item.data.id
    );

   // ...
}