  The caustic technique for measuring mass profiles of galaxy clusters relies
on the assumption of spherical symmetry. When applied to aspherical galaxy
clusters, the method yields mass estimates affected by the cluster orientation.
Here we employ mock redshift catalogues generated from cosmological simulations
to study the effect of clusters intrinsic shape and surrounding filamentary
structures on the caustic mass estimates. To this end, we develop a new method
for removing perturbations from large-scale structures, modelled as the
two-halo term, in a caustic analysis of stacked cluster data.
  We find that the cluster masses inferred from kinematical data of ~10^14 Msun
clusters observed along the major axis are larger than masses from those
observed along the minor axis by a factor of 1.7 within the virial radius,
increasing to 1.8 within three virial radii. This discrepancy increases by 20%
for the most massive clusters. In addition a smaller but still significant mass
discrepancy arises when filamentary structures are present near a galaxy
cluster.
  We find that the mean cluster mass from random sightlines is unbiased at all
radii and their scatter ranges from 0.14 to 0.17 within one and three virial
radii, with a 40% increase for the most massive clusters. We provide tables
which estimate the caustic mass bias given observational constraints on the
cluster orientation.
