Have you tried
unticking the box for 'Straighten descendant branch lines where possible' (in the More Layout Options dialog)?

This from the Help for More Layout Options Dialog:
Straighten descendant branch lines where possible: If this box is checked, spouse boxes will be taken into account when centring children below their parents.
This may mean that the line connecting parents to their child has a kink in it. But descendant branches as a whole will be much straighter - especially when displaying a single line of descendant over several generations.