If these thin blue `ratlines` or `airlines` do not disappear if you save the file, close it and reopen it then, without being able to see your project, I would guess that you have routed traces to different sets of pins but which have the same netname. If you zoom in or click on the traces you will see their net names. You can edit these names in the right hand panel. To avoid this kind of error please see: https://easyeda.com/forum/topic/How_does_the_Connect_Pad_to_Pad_tool_work_-JgQO0Ay7H Please also see: https://easyeda.com/forum/topic/The_best_way_to_design_a_PCB_in_EasyEDA-ThR3pwqIC