Where do Xamarin bugs get reported?
In the latest version of Forms 4 (as of yesterday), the problem I am seeing:
ListView has a pull to refresh. Seems okay, unless the user scrolls down the list, then returns to the top and then performs a pull to refresh. The list rendering is completely broken. It might render some or none of the list. If you then scroll around some more, it starts to fill in parts of the list.
Another problem which is harder to reproduce, is the first time the list is rendered only 2/3 of it are drawn.
Work around for now is to revert to Forms 3.6, not problems there.