Eigenvectors of a symmetric complex matrix matrix fail to form a complete basis

Question

I am required to diagonalize a particular symmetric complex matrix $M$ given by these data.

The matrix has distinct eigenvalues and orthogonal eigenvectors.

But the (normalized) eigenvectors do not seem to follow the completeness relation $\sum_i{\bf v}_i{\bf v}_i^T={\bf I}$.

As a test, I built a separate random symmetric complex matrix then diagonalized it. The completeness relation is satisfied in this case.

I really am puzzled and would appreciated any insight.

Thanks in advanced!

P/S: The link data contains:

1. M_Re.csv which is the real part of $M$,
2. M_Im.csv which is the imaginary part of $M$,
3. Diag.nb which is the Mathematica codes for doing the computation (you don't have to use it if you prefer some other software).