  The nucleus of the planetary nebula Hen2-428 is a short orbital-period
(4.2h), double-lined spectroscopic binary, whose status as a potential
supernova type Ia progenitor has raised some controversy in the literature.
With the aim of resolving this debate, we carried out an in-depth reanalysis of
the system. Our approach combines a refined wavelength calibration, thorough
line-identifications, improved radial-velocity measurements, non-LTE spectral
modeling, as well as multi-band light-curve fitting. Our results are then
discussed in view of state-of-the-art stellar evolutionary models.
  Besides systematic zero-point shifts in the wavelength calibration of the
OSIRIS spectra which were also used in the previous analysis of the system, we
found that the spectra are contaminated with diffuse interstellar bands. Our
Voigt-profile radial velocity fitting method, which considers the additional
absorption of these diffuse interstellar bands, reveals significantly lower
masses ($M_1=0.66\pm0.11M_\odot$ and $M_2=0.42\pm0.07M_\odot$) than previously
reported and a mass ratio that is clearly below unity. Our spectral and light
curve analyses lead to consistent results, however, we find higher effective
temperatures and smaller radii than previously reported. Moreover, we find that
the red-excess that was reported before to prove to be a mere artifact of an
outdated reddening law that was applied.
  Our work shows that blends of HeII 5412A with diffuse interstellar bands have
led to an overestimation of the previously reported dynamical masses of
Hen2-428. The merging event of Hen2-428 will not be recognised as a supernova
type Ia, but most likely leads to the formation of a H-deficient star. We
suggest that the system was formed via a first stable mass transfer episode,
followed by common envelope evolution, and it is now composed of a post-early
AGB star and a reheated He-core white dwarf.
