  Background: Asymmetric fission is known to occur in two regions, the
actinides and sub-lead, and is dependent on the fissioning system excitation
energy. Experimental evidence in the sub-lead region show that this mode is
surprisingly persistent with increasing energy and its origin is not fully
understood.
  Purpose: To experimentally study the fusion-fission reaction of $^{215}$Fr at
moderate excitation energy and determine previously unknown independent fission
yields and other properties.
  Method: The compound nucleus was formed in the reaction $^{18}$O +
$^{197}$Au. The prompt gamma-rays emitted during the reaction were measured
with the high efficiency and high granularity $\nu$-ball2 spectrometer.
Independent fission yields of even-even nuclei were determined by detecting
triple-gamma cascades in the fission fragments.
  Results: The observed yields, although dominated by a symmetric peak, show
maxima for heavy fragment of $Z \approx 54-56$, which is consistent with the
known results in the actinide region but unexpected for the nuclide of
interest, and at the studied excitation energy.
  Conclusions: The mode of asymmetric fission is present even at relatively
high excitation energies in the system studied. This observation matches
experimental findings in the sub-lead region, contrary to the actinides, and so
far there is no well-developed explanation of this phenomenon.
