The console reports: Error in parsing value for ‘left’. Declaration dropped. Error in parsing value for ‘top’. Declaration dropped. A little debugging shows

The console reports: Error in parsing value for ‘left’. Declaration dropped. Error in parsing value for ‘top’. Declaration dropped. A little debugging shows that a NaN is getting into the item properties and then propagating through the calculations until it gets to the style.left= line where it fails, preventing the item from moving. Resizing the window will make everything start working.