Created attachment 147698 [details]
IDE log

Thanks for reporting,

it is always very useful to have some sample project or example to reproduce the issue. Can you attach it?

Can you please explain what tree structure and what iterator are you talking about? A code sample is really welcomed.

I've tested Variable window when stepping through program like this:

        List<String> list = Arrays.asList(new String[] { "a", "b", "c", "d" });
        Iterator<String> iterator = list.iterator();
        while (iterator.hasNext()) {
            String next = iterator.next();
            System.err.println(next);
        }

and did not find anything unusual.
Thanks for your clarification...