  We describe an aberration of the resampling estimator for the Green's
function customarily used in hybridization expansion continuous-time quantum
Monte Carlo. It occurs due to Pauli principle constraints in calculations of
Anderson impurity models with baths consisting of a discrete energy spectrum.
We identify the missing Feynman diagrams, characterize the affected models and
discuss implications as well as solutions. This issue does not occur when using
worm sampling or in the presence of continuous baths. However certain energy
spectra can be inherently close to a discrete limit, and we explain why
autocorrelation times can become very large in these cases.
