Angular Material binding to event cancels valueChanges subscription

I have a pretty basic autocomplete set up with Angular Material (6). Here is the basic implementation:

<mat-form-field>
    <input type="text" matInput placeholder="Company" formControlName="company" [matAutocomplete]="autoCo"/>
    <mat-autocomplete #autoCo="matAutocomplete" [displayWith]="displayCo">
        <mat-option *ngFor="let company of filteredCompanies | async" [value]="company">
            
        </mat-option>
    </mat-autocomplete>
</mat-form-field>

That works without a problem. However, I want to have something happen when a selection is made. To do this, I added (optionSelected)="onSelectionChanged($event)" to the mat-autocomplete element. Initially, everything works as expected (filtering the options works). When a selection has been made, the onSelectionChanged function also fires as expected.

However, after a selection has been made, the selected item is the only item available in the autocomplete drop-down no matter what changes I make. So even if I delete all the text in the input, I still only see the previously selected option. I would expect to see the complete list instead.

In ngOnInit, I have:

this.filteredCompanies = this.companyForm.get("company").valueChanges.pipe(
        debounceTime(200))
        .pipe(mergeMap(val => this.filter(val)));

It appears that the valueChanges subscription ends if I bind to optionSelected. If I don't bind to optionSelected, the list of options updates as expected.

Am I incorrectly binding to the optionSelected event? Do I have to re-subscribe to the form valueChanges from within onSelectionChanged()?? If so, why?

For what it is worth, here is some other relevant code:

@Output()
optionSelected = new EventEmitter();

onSelectionChanged(event: any) {
    console.log(event);
    this.optionSelected.emit(event);
}

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