When dragging a vector path more than 10,000 pixels from the top of the image, it disappears. It's still there, near as I can tell, but can't be seen. When moving it with arrow keys it seems to work but disappears on save and reload. I tried a copy-paste at the line, and it cuts the visible part of the path where the edge is.
I don't expect a fix, considering you have to change the config just to get the program to let you make an image this big, but does anyone have a workaround better than overlapping the whole image on two layers and then moving it down with shift every save?