Smartfill rules

Hi

I am currently making a map using Corel Draw. The idea is to define lihological unit boundaries using the freehand tool overlain a imported topographic bitmap and filling in with a transparent color.

However, there are some issues filling in the areas between the lines as the smartfill seems to define an area by different parameters than what my intuition dictates.

Point is, instead of filling in one area bounded by the freehand tool it will fill two or more, apparently depending on how the last line was drawn. There seems to be some underlying rules that I do not grasp.

For a while I Blamed it on not properly joining lines, but "view wireframe" and "join curves" seem to suggest otherwise.

Wisdom and suggestions would be much appreciated.

Regards
EK

PS. Would have liked to upload the file, perhaps minus the bitmap for size, but there seems to be no intuitive way to attach a file.