John, WED newbie here myself, currently working through Jan Vogel's excellent WED tutorials on YouTube, updating ENCN and hoping to submit to the gateway...
I had this error yesterday funnily enough, think I was placing a Forest at the time, basically I think it's a warning that one of your sides of your object is crossing another or overlapping? If you do the export and when the error pops, if you check the right hand "objects" pane then I think the offending item will be highlighted. I just selected and zoomed right in and check all my node positions and lines, made some adjustments and it was fine then.
Hopefully that will work for you?