Dragged element disappear when model.nodeDataArray changed

Hi,I use this sample https://gojs.net/latest/samples/planogram.html ,the different is that I load node data from server side.but I have a problem:the right Diagram node data I load from the server side,and load every 5 seconds.when user drag a element from the left Diagram(has not drop it),and at the same time,the load function occurs,then the dragged element will disappear.
Im not sure if I description the problem.Looking forward to your reply,thank you!