  We present a precise measurement of double-polarization asymmetries in the
$^3\vec{\mathrm{He}}(\vec{\mathrm{e}},\mathrm{e}'\mathrm{d})$ reaction. This
particular process is a uniquely sensitive probe of hadron dynamics in
$^3\mathrm{He}$ and the structure of the underlying electromagnetic currents.
The measurements have been performed in and around quasi-elastic kinematics at
$Q^2 = 0.25\,(\mathrm{GeV}/c)^2$ for missing momenta up to
$270\,\mathrm{MeV}/c$. The asymmetries are in fair agreement with the
state-of-the-art calculations in terms of their functional dependencies on
$p_\mathrm{m}$ and $\omega$, but are systematically offset. Beyond the region
of the quasi-elastic peak, the discrepancies become even more pronounced. Thus,
our measurements have been able to reveal deficiencies in the most
sophisticated calculations of the three-body nuclear system, and indicate that
further refinement in the treatment of their two- and/or three-body dynamics is
required.
