It's by design. It's still possible to see all items in available space, even if not full height is available but only minimal height.
You can see that on your video. Last item "David Jackson" is visible even when you see only half of expanded list.
We have tried it but it seems it is not working for our case. We are overriding the combo behaviour and filling the store with picklist entries while the user is typing. For this reason, the first time the picker is rendered it has 0 entries so it fits downwards in our screen.
The problem comes after adding more values because the picker is not re rendered completely so the position is wrong.
We have a workaround which is hiding and showing the picker after updating the store but the visual result is not the best. Is there any way of forcing it to completely render (and chose a new position) without hiding it?
My bad! But something seems weird here. Now all the values are getting displayed when scrolling through the picker but for some reason Bryntum always decide to render downwards except I start scrolling up through the page