Possibly the same case as in http://netbeans.org/bugzilla/show_bug.cgi?id=200846

Having Outline with a large model (FixedHeightLayoutCache), expanding a node fires an event with firstRow=0 and lastRow=0 of type INSERT. This then produces a call to SelectionModel.insertIndexInterval(0, 1, true) which shifts the whole selection.

My assumption about the cause follows:

EventBroadcaster.translateEvent method checks for firstRow == -1. Before, it adds one to the result. As FixedHeightLayoutCache returns -1 for collapsed nodes, it seems the condition firstRow == -1 can never be true with FixedHeightLayoutCache.