Cosmography and flat $\Lambda$CDM tensions at high redshift
  Risaliti, Lusso \& collaborators have constructed a high-redshift Hubble
diagram of supernovae (SNe); quasars (QSO) and gamma-ray bursts (GRB) that
shows a "$\sim 4 \, \sigma$ tension with the $\Lambda$CDM model" based on a log
polynomial cosmographic expansion (Risaliti et.al 2018, Lusso et.al 2019). In
this work, we demonstrate that the log polynomial expansion generically fails
to recover flat $\Lambda$CDM beyond $z \sim 2$, thus undermining the $\sim 4 \,
\sigma$ tension claim. Moreover, through direct fits of both the flat
$\Lambda$CDM and the log polynomial model to the SNe+QSO+GRB dataset, we
confirm that the flat $\Lambda$CDM model is preferred. Ultimately, we trace the
tension to the QSO data and show that a best-fit of the flat $\Lambda$CDM model
to the QSO data leads to a flat $\Lambda$CDM Universe with no dark energy
within $1 \, \sigma$. This marks an irreconcilable tension between the
Risaliti-Lusso QSOs and flat $\Lambda$CDM.
