Jeffery, thanks for the reply and check on my logic.
Through some iterations I lost track and conflated NOT NULL and DEFAULT value that was in the original iteration.
The...

This is actually looking like some type of AOG issue at least loosely.
Others working on this issue have found that by removing the AOG the queries work fine.  Recreate...

A few quick questions to consider:

• What is the reason to use surrogate keys rather than natural keys?
• Should relationships between tables use different data types?  (User.UserKey int / UserSite.UserKey...

Are you connecting the computer 1 instance?  Or are you attempting to use the same .mdf file as on multiple instances (2, 3, 4, and 5)?
Each SQL Server instance...

What user mode is the database in?
SELECT    d.name
    ,    d.user_access_desc
FROM    sys.databases AS d
;

As Luis pointed out, you'll want to fully qualify the column names.  Essentially, the [date] column is used by more than one table and SQL Server does not know...

When doing bulk load with a lot of data, i.e. data warehouse, it can be turned off to improve performance.
Couple of write ups on the topic:
http://www.sqlservercentral.com/blogs/waterox-sql/2014/10/17/untrusted-foreign-keys/

Your comment about 24x values, are you looking for 24 hours?  It appears that you are selecting 48 hours of data.
Either update the @enddate or remove the DATEADD() if...