  GRB160203A is a high redshift long gamma-ray burst presenting a collection of
unusual features in the afterglow light curve. We study its optical and X-ray
data. We find this event to occur within a constant density medium during the
first part of the afterglow. However, after 13 ks we spot some flaring
activities in the optical and X-ray light curves. We explain these flares by
fluctuation of densities of the surrounding medium. Other scenarios, such as
energy injection from a magnetar or variation of microphysical parameters are
not supported by the data. We tentatively link these fluctuations to an unusual
host galaxy, with gas density similar to the Milky Way and a dense cocoon of
matter around a stellar progenitor similar to a Wolf-Rayet star. A termination
shock scenario is found to be less likely.
