Denote the spectral factorization of A as
A = Q S Q^T,
where S is the diagonal matrix of eigenvalues and Q is the orthogonal matrix whose columns are the eigenvectors.
Then DSYEV produces an S whose diagonal elements are in ascending order, whereas, I presume, that pcacov produces an S whose diagonal elements are in descending order. If you try the MATLAB function eig you will see that it produces the same output as you achieved for DSYEV.
So you need to permute the output from DSYEV if you wish to have the columns of Q corresponding to the eigenvalues in descending order.
A = (Q P) (P^T S P) (Q P)^T,
where P is the permutation matrix.
In your second example you have two (nearly) equal eigenvalues. Eigenvectors corresponding to equal eigenvectors are not unique. Think of the unit matrix for which any vector is an eigenvector (I x = 1 x for any x). The two relevant columns from pcacov and DSYEV span the same subspace.
Hope that helps. Best wishes,