When you create or load an animation and first you click on the headline of the timeline (the ruler with the frame numbers, not the actual layers) and drag the cursor, it behaves strangely: the previous cursor is not erased, and a new duplicate cursor image placed on the touched frames.
The reason for this: before you click on a layer at least once, the index structure of the selected row is in invalid status and it returns -1 for its row() value. So the setCurrentIndex() function cannot replace the cursor correctly. My solution is used many times elsewhere in the same source file.