The dotted "crossing lines" only appear in All Relatives Diagrams and are dependent on each individual tree. In your example James John TAYLOR, being the youngest child of John & Phoebe, is correctly placed to the left of his younger siblings. But FH has determined that to link him to his wife in that location would, due to other individuals in the tree and their relationships, mean that the diagram would need a much larger area to be displayed in, and may become more complex and difficult to visualise in other ways. So it creates a "proxy box" as the original location for James, and moves his primary box to a suitable location where he can be placed next to his wife, her ancestors and their children without greatly increasing the overall size of the diagram.
If you had created the chart with the individuals displayed within their own boxes, you would find that the box for James in its original location to the left of his siblings would be greyed out (a proxy box), with the connecting line (the dotted line) linking it to a fully formed box next to his wife. By not displaying the individuals within boxes, the proxy and new locations for James are less obvious.
Crossing lines only appear in All Relatives diagrams, and I don't think they can be turned off. It might be possible to eliminate the crossing line by experimenting with moving James to a different location (dragging his "box" around the diagram) but you may find that has other more undesirable consequences.
Another alternative would be to use the Ancestor and Descendant diagram, rather than the All Relatives Diagram. It rather depends on the extent of the tree you are trying to show.
If you want expert help with FH, you might want to try the Family Historian User Group forum at
https://www.fhug.org.uk/forum/index.php
