  The oscillatory magnetoresistance spectrum of the organic metal
(BEDO)$_5$Ni(CN)$_4\cdot$3C$_2$H$_4$(OH)$_2$ has been studied up to 50 T, in
the temperature range from 1.5 K to 4.2 K. In high magnetic field, its Fermi
surface corresponds to a linear chain of quasi-two-dimensional orbits coupled
by magnetic breakdown (MB). The scattering rate consistently deduced from the
data relevant to the basic $\alpha$ and the MB-induced $\beta$ orbits is very
large which points to a significant reduction of the chemical potential
oscillation. Despite of this feature, the oscillations spectrum exhibits many
frequency combinations. Their effective masses and (or) Dingle temperature are
not in agreement with either the predictions of the quantum interference model
or the semiclassical model of Falicov and Stachowiak.
