Good catch Lynn. But I don't think just changing to ROW_NUMBER fixes the tie-break problem. It just returns one row and who knows what the tie-breaker is? So whether using RANK, ROW_NUMBER, or perhaps DENSE-RANK, I should have added a tie-breaker to the ORDER BY like this:

RANK() OVER (ORDER BY EndDate DESC, ID DESC) AS [Rank]

This would give the tie-break to the most recently added row...but other ways of breaking the tie might be better such as a full DATETIME2 date.