There is an ‘offset’ cut area beside my drain.

Symptoms:

When burning a drain profile into a surface, one or more side cut areas appear that seem disconnected with the actual drain path. 

Cause:

The side batter from the drain rises up through an existing surface that undulates in such a way that both cut and no-cut areas result.

Solution:

Increase the batter angle, or smooth the field surface before creating the drains (and create the drains based on the DESIGN, not the ORIGINAL surface). Alternatively, simply ignore the offset cut area.