  The study of planet occurrence as a function of stellar mass is important for
a better understanding of planet formation. Estimating stellar mass, especially
in the red giant regime, is difficult. In particular, stellar masses of a
sample of evolved planet-hosting stars based on spectroscopy and grid-based
modelling have been put to question over the past decade with claims they were
overestimated. Although efforts have been made in the past to reconcile this
dispute using asteroseismology, results were inconclusive. In an attempt to
resolve this controversy, we study four more evolved planet-hosting stars in
this paper using asteroseismology, and we revisit previous results to make an
informed study of the whole ensemble in a self-consistent way. For the four new
stars, we measure their masses by locating their characteristic oscillation
frequency, $\mathrm{\nu}_{\mathrm{max}}$, from their radial velocity time
series observed by SONG. For two stars, we are also able to measure the large
frequency separation, $\mathrm{\Delta\nu}$, helped by extended SONG single-site
and dual-site observations and new TESS observations. We establish the
robustness of the $\mathrm{\nu}_{\mathrm{max}}$-only-based results by
determining the stellar mass from $\mathrm{\Delta\nu}$, and from both
$\mathrm{\Delta\nu}$ and $\mathrm{\nu}_{\mathrm{max}}$. We then compare the
seismic masses of the full ensemble of 16 stars with the spectroscopic masses
from three different literature sources. We find an offset between the seismic
and spectroscopic mass scales that is mass-dependent, suggesting that the
previously claimed overestimation of spectroscopic masses only affects stars
more massive than about 1.6 M$_\mathrm{\odot}$.
