To repro:Define a FK relationship.
Deploy the database.
Change the cascade behavior of the FK relationship.
Deploy the database. SQL Server complains that you can't Alter--you must drop and recreate with the desired cascade behavior.
Workaround:
Delete the FK relationship in DDT.
Deploy the database.
Create the FK relationship again with the desired cascade behavior.
Deploy the database.
Permanent solution:
DDT should understand that a change in cascade behavior requires the FK to be dropped and recreated and just do that.
Thanks!