  Monoclinic Li$_3$Co$_2$SbO$_6$ has been proposed as a Kitaev spin liquid
candidate and investigated intensively, whereas the properties of its
polymorph, the orthorhombic phase, is less known. Here we report the magnetic
properties of the orthorhombic Li$_3$Co$_2$SbO$_6$ as revealed by dc and ac
magnetic susceptibility, muon spin relaxation ($\mu$SR) and neutron diffraction
measurements. Successive magnetic transitions at (115, 89 and 71) K were
observed in the low field dc susceptibility measurements. The transitions below
$T_N$ (= 115 K), are suppressed in higher applied fields. However, zero field,
ac susceptibility measurements reveals distinct frequency independent
transitions at about (114, 107, 97, 79 and 71) K. A long range magnetic ordered
state was confirmed by specific heat, $\mu$SR and neutron diffraction
measurements, all indicating a single transition at about 115 K. The
discrepancy between different measurements is attributed to possible stacking
faults and/or local disorders of the ferromagnetic zig-zag chains, resulting in
ferromagnetic boundaries within the overall antiferromagnetic matrix.
