It shouldn't. The only way I can see that making a difference is if you're filtering the report based on who's running/reading it (using a filter on the username).
You...

That looks normal. You don't have any filters on the subreport, do you?
What happens if you make the parameters for the subreport visible (temporarily) and open it by itself?...

Why not use LAG() to get the previous ship date for a tracking number?  This is ugly, but I think it'll work:
SELECT x.tracking_number
    , x.ship_date
    ,...

This is close...

CREATE TABLE #tblA (
    Yr INT
    ,Title CHAR(3)
    ,Country CHAR(2)
    ,Age TINYINT
);
CREATE TABLE #tblB (
    Yr INT
    ,Title CHAR(3)
    ,Country CHAR(2)
    ,Age TINYINT

This sounds like a job for PowerShell
https://community.spiceworks.com/topic/468653-powershell-script-to-remove-the-password-never-expires-in-ad-to-users-in-a-file

You'd be able to tell because when you drop the field on the wrong report, you'd get something like
= FIRST(DataSetName!FieldName.Value)

instead of just the fieldname.
=FieldName.Value

I...

I used to work in healthcare, so I totally understand the confidentiality stuff. (Taking the Good Clinical Practices exam after looking at what they were doing nearly gave me a...

What kind of visual are you using for the subreport? Is it a tablix? I would test it by creating a simple tablix and populating it and see if you...

Why can't you use a function?
I'd use DelimitedSplit8K and be done... Why the arbitrary requirement? Is this a class assignment or something?.

Not sure how you would end up with only one record in your subreport.  Are you using a parameterized stored procedure as the source for your subreport's dataset? Does the...

You probably have to shrink it, but then you'll have to rebuild all the indexes... Good thing it's Friday... might be done by Monday.

Did you try using a CASE statement?