Treetable always executing 2 network requests on collapse/expand?

We've been using the Treetable in Vaadin 6 and now migrated to Vaadin 7. 

CONFIGURE NETWORK BEHAVIOUR?
In Vaadin 6 the tree table most of the time issues one network request when a node is opened/closed.
In Vaadin 7 it seems to always do at least 2 requests (also visible in Sample: https://demo.vaadin.com/sampler/#ui/grids-and-trees/tree-table)

Requests
[["32", "v", "v", ["toggleCollapsed", ["s", "72"]]]]
[["32", "v", "v", ["firstToBeRendered", ["i", 0]]], ["32", "v", "v", ["lastToBeRendered", ["i", 27]]],…]

==> Is there a way to configure the table that it does less requests in Vaadin 7?

JUMPING ON EXPAND/COLLAPSE
On expand/collapse the table is jumping (only happens if the top of the table is not visible, mean we've scrolled down a bit). Actually is looks like after the first network request, something in the view changes (everything going up) and the after processing the second request, it all goes back where it should be. Such a behaviour can be seen in a very minimal manner (1..2 pixels) in the Sampler too. In our case it can be 50 pixels which confuses the users, even if it goes back to the initial position after the 2nd request.

Thanks for any input!