When using the the sample project provided with the 4.6 beta, I was looking into the scene called "widgets", when using the selection list I noticed that occasionally items would be inconsistently greyed out, e.g if I selected first then second would be greyed out, if I then selected second then second and third would be greyed out. However the order is not always the same, but this bug is easy to reproduce by selecting the list items in any random order.