Only check the checkbox if the value of ngModel is true

When my checkbox is clicked the value of my ngModel produto.checked is set to true, but in a moment this value is changed to false without a click in the checkbox. How can i make my checkbox only check/uncheck according by my ngModel?

I try something like:

<tr *ngFor="let produto of sortedDataProduto; let i = index">
   <input [checked]="produto.checked" [(ngModel)]="produto.checked" name="checkedproduto" type="checkbox">
</tr>