First of all, to call the GP Editor you double click on the poly/line or select it with the mouse, right-click and select "Edit" from the context menu.
It's not clear how you created those GPs, but I'm not surprised they won't compile. Examine one of them in the GP Editor (i.e. call the GP Editor). You'll notice in addition to the line outline there is a lonely vertex at the bottom left-hand corner of the texture. That's what is causing the difficulty. Unfortunately, there's no delete function in the GP editor. So, the only solution is to delete and re-create those lines in ADE.
To create the new lines, first draw the new GP line with ADE. The GP editor will open automatically. Specify the width, select the texture and, before doing anything else, select Parking Double Row in the Line/Pattern style combo box. Adjust the vertices as necessary and click OK, Since all 4 lines are identical, it's a simple copy and paste for the others