Thank you for reporting us these issues. We will fix the maximize problem as soon as we can. The fix will be included in one of the next latest internal builds.
The second problem is not really a bug, but expected behavior - as the Width and Height of the Window are initially double.NaN, it will be as big as its content needs to be. The strange behavior happens because of the UserControl in it. If you resize the window its width and height are explicitly set and its content cannot resize it any more.
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