Does not automatically select first matching item in ListView

[WheelsNotRound]

The popped-up list view is correctly showing the items matching the input text, but the first item in the list is not selected.
This means you must use the down arrow key to select it, before then using Tab or Enter to finish the auto-complete.

The experience I was after is like VS, whereas the first item is auto-selected, and you just type the first key characters followed by TAB to finish the auto-complete.

I am using the latest Scintilla control available as a Nuget package (5.3.2.9).

The strange thing is that on the Test apps in this solution, certain Demo forms auto select the first item, but some do not.
I'm relatively new to c#, and cannot see in this package where the list is first displayed, and how or why the first item in the list would be highlighted or not.
I am able to force the first item to be highlighted in my app sending a down key stroke inside this controls 'Opening' event, but any subsequent key strokes result in the first item being un-highlighted, and as there is not other event I can hook into, I cannot restore the highlighting of the first item until the list view is re-opened on a new Opening event.

The behaviour between the demo apps does seem inconsistent. Any ideas where I can look or where is could be broken?

The SearchPattern property is set to [\w.] and changing this makes no difference.
I have also tried matching case, or using just digits in the item list, but neither of these changes made any difference.