drop down attached to dataset filter not working correctly

I have 2 dropdown controls. The first is contains values that allows a dataset to be filtered by key. The second is associated with a dataset and when the first is changed i apply a filter to the dataset for the second dropdown control. When the filter is applied the value in the second dropdown correctly changes but when i select the dropdown, there are still items in there that should have been removed.

export function dropdown1_change(event,$w) {
$w(‘#dataset1’).setFilter(wixData.filter().eq(‘title’, $w(‘#dropdown1’).value));
}

if i execute the following

console.log($w(“#dataset1”).getTotalCount()); i get 1 item which is correct

What am i missing to remove rows from the dropdown control?