  The contribution of the light-front valence wave function to the
electromagnetic current of spin-1 composite particles is not enough to warranty
the proper transformation of the current under rotations. The naive derivation
of the plus component of the current in the Drell-Yan-West frame within an
analytical and covariant model of the vertex leads to the violation of the
rotational symmetry. Computing the form-factors in a quasi Drell-Yan-West frame
$q^+\rightarrow 0$, we were able to separate out in an analytical form the
contributions from Z-diagrams or zero modes using the instant-form cartesian
polarization basis.
