Pencil 2 Brush disappeared
I drew a stroke with the Pencil 2 Brush. After duplicating the artboard, I noticed my strokes had disappeared. The path was still there, though - as was the applied Brush 2. However, even in the brushes panel, Pencil 2 seemed to have no attributes. It was just blank, not even showing a sample/preview stroke. I changed the path to Pencil 1, and all was fine. Though, several days later Pencil 2 brush is still missing.