I found a bug in Wwise code:
I need \Assets\Wwise\Editor\WwiseWindows\AkWwiseTreeView.cs to be updated:
for (var i = 0; i < in_item.Items.Count; i++)
in_item.IsHidden = false;
in_item.IsSelected = false; // Sally Fix: (Added) This needs to remove the previous selection after filter.
When you search, then select, then search for another entry, the previous entry is selected.
I fixed this by adding "IsSelected = false;" in the Wwise run-time code.
I can provide a full test-case if necessary.