Angular distributions of the two ejected electrons resulting from the double ionization of helium by electron impact have been measured by means of a multicoincidence multiangle (e,3e) spectrometer at an incident energy of about 0.6 keV and equal outgoing energies Eb=Ec=11 eV. We identify various regimes of kinematical parameters where substantial differences are found with respect to the first-Born convergent close-coupling calculations: an angular shift of the position of the main lobe and the presence of additional lobes. These differences are attributed to high-order contributions in the projectile-target interaction. This conclusion is supported by recent (e,3e) calculations performed within the second-Born approximation.