Thank you for reporting this issue. To help avoid this behavior, please use the layer menu options in the 'Legend' for 'Move up' and 'Move down' instead of dragging the layers around. This behavior seems to depend on available network speed, and using the menu options will help make sure one layer has completed moving before another is moved.
解决办法
Create a new map with new map area sites or geography.
Move the order of the layers slowly in the map content for the changes to be honored in the legend.
After the sites are above the legend, export the map as a PDF file.