This problem may be related to the one reported here:
Though this case is a bit different.
Building off of the virtual scrolling from local data example, if a single row is added to that grid, the scrolling stops working:
Press either button at the top of the grid to add a row and cause the scrolling to fail.
Note that both the native create ("Add new record") and the custom "copy first row" buttons both cause the scrolling to fail.
Is there any solution or workaround to this problem?