Sometimes when I edit the 2d display of a plant symbol several lines show up once I exit the symbol edit that weren't there before. For example, if I create a plant symbol and simply make it one circle, when I exit the edit mode there will about 4 or 5 overlapping circles. If I go back to the edit screen only the original circle will be visible and editable but the extra lines will still show up every time I exit the edit screen. I haven't been able to remedy the problem. Once a symbol gets infected with the extra lines there doesn't seem to be anything I can do to get rid of them, even if I delete all the line work and start again. It doesn't appear to be a class issue as I've tried changing class designations and visibility repeatedly with no results. The only solution I've found is to create a whole new symbol from scratch, which kind of undermines the convenience of the symbol if it won't stay consistent.
A solution to the problem would be ideal, but at this point I'd just be happy to know what's causing it so I can try to avoid it in the future.
First picture is in the 2d edit mode and the second shows the symbol in the design layer. All classes and layers are turned on in both pictures.