Hi Colin

Thanks for reaching out in the Lucidchart Community! When it comes to move objects/tables around the canvas smart lines behave differently in ERDS as compared to other diagrams. Since lines in ERDs refer to the relationship between specific fields in two tables when one of those tables is moved the line doesn't automatically adjust its connection points to form the most efficient path between the two objects because this could mean connecting to a different field. Thus keeping the line anchored to a specific field/point when moving tables prevents smart lines from changing the intended connection between correlated fields. 

To go over the details of how to create entity relationship diagrams with customized text styling and relationships between fields Id' recommend taking a look at the Entity Relationship Diagrams (ERDs) article from the Lucidchart Help Center and for more information on how to format lines reviewing our Work with Lines article.

Hope this helps! Please let me know if you have any further questions.