  The thermal fit to preliminary HADES data of Au+Au collisions at
$\sqrt{s_{_{NN}}}=2.4$ GeV shows two degenerate solutions at $T\approx50$ MeV
and $T\approx70$ MeV. The analysis of the same particle yields in a transport
simulation of the UrQMD model yields the same features, i.e. two distinct
temperatures for the chemical freeze-out. While both solutions yield the same
number of hadrons after resonance decays, the feeddown contribution is very
different for both cases. This highlights that two systems with different
chemical composition can yield the same multiplicities after resonance decays.
The nature of these two minima is further investigated by studying the
time-dependent particle yields and extracted thermodynamic properties of the
UrQMD model. It is confirmed, that the evolution of the high temperature
solution resembles cooling and expansion of a hot and dense fireball. The low
temperature solution displays an unphysical evolution: heating and compression
of matter with a decrease of entropy. These results imply that the thermal
model analysis of systems produced in low energy nuclear collisions is
ambiguous but can be interpreted by taking also the time evolution and
resonance contributions into account.
