Steps to Reproduce

run the attached example it will update the listmodel every 2 seconds by appending an item
Continuously change the scroll position
Depending on timing the listbox sometimes shows a blank area.

This recording https://www.screencast.com/t/DlcP35nobja shows the problem after 0:45

Actual Result

the scroll position gets out of sync with the top padding

Expected Result

correctly updating visible area according to the scroll position

Debug Info

usually the 3 events onScrollPos, onDataLoading, onTopPad are sent in a single request to the server in order to update the currently visible area.

Somehow the onTimer event affects the event sequence and those 3 events get sent in separate requests.
If onTimer event-listener updates the model (e.g. appending an item) this sometimes leads to incorrectly calculated ROD offset and topPad values.