Need a lot more information.   Could be any of a number of things.   Exactly what version of Visual Studio was the package originally created in?   Exactly what version of Visual...

I'm fairly certain you are asking for far more effort than is reasonable for a forum post response, and that is likely the reason for no response as yet.   I'm...

First order of business was to correct the data.   Any of a number of rows had data issues, and the death date required update for George H.W. Bush from NULL...

Sounds to me like page splits are likely here, and in large quantities.    Might be worth taking a look into the number of varchar columns (or nvarchar) and see...

This at first seemed like there just wasn't any good description of the exact rule for choosing a given row.
So I kept reading along, and then found what may...

Okay, so what, pray tell, can we possibly help with?   We have no information about the package itself beyond it's "variable performance", and zero level of detail about it or...