  Recently, two independent groups found very different results when measuring
the central velocity dispersion of the galactic globular cluster NGC 6388 with
different methods. While L\"utzgendorf et al. (2011) found a rising profile and
a high central velocity dispersion (23.3 km/s), measurements obtained by
Lanzoni et al. (2013) showed a value 40% lower. The value of the central
velocity dispersion has a serious impact on the mass and possible presence of
an intermediate-mass black hole at the center of NGC 6388. We use a photometric
catalog of NGC 6388 to create a simulated SINFONI and ARGUS dataset. The
construction of the IFU data cube is done with different observing conditions
reproducing the conditions reported for the original observations as closely as
possible. In addition, we produce an N-body realization of a 10^6 M_SUN stellar
cluster with the same photometric properties as NGC 6388 to account for
unresolved stars. We find that the individual radial velocities, i.e. the
measurements from the simulated SINFONI data, are systematically biased towards
lower velocity dispersions. The reason is that due to the wings in the point
spread function the velocities get biased towards the mean cluster velocity.
This study shows that even with AO supported observations, individual radial
velocities in crowded fields are likely to be biased. The ARGUS observations do
not show this kind of bias but were found to have larger uncertainties than
previously obtained. We find a bias towards higher velocity dispersions in the
ARGUS pointing when fixing the extreme velocities of the three brightest stars
but find those variations are within the determined uncertainties. We rerun
Jeans models and fit the kinematic profile with the new uncertainties. This
yields a BH mass of M_BH = (2.8 +- 0.4) x 10^4 M_SUN and M/L ratio M/L = (1.6
+- 0.1) M_SUN/L_SUN, consistent with our previous results.
