  Fast Radio Bursts (FRBs) are short-timescale transients of extragalactic
origin. The number of detected FRBs has grown dramatically since their
serendipitous discovery from archival data. Some FRBs have also been seen to
repeat. The polarimetric properties of repeating FRBs show diverse behaviour
and, at times, extreme polarimetric morphology, suggesting a complex
magneto-ionic circumburst environment for this class of FRB. The polarimetric
properties such as circular polarisation behaviour of FRBs are crucial for
understanding their surrounding magnetic-ionic environment. The circular
polarisation previously observed in some of the repeating FRB sources has been
attributed to propagation effects such as generalised Faraday rotation (GFR),
where conversion from linear to circular polarisation occurs due to the
non-circular modes of transmission in relativistic plasma. The discovery burst
from the repeating FRB$~$20180301A showed significant frequency-dependent
circular polarisation behaviour, which was initially speculated to be
instrumental due to a sidelobe detection. Here we revisit the properties given
the subsequent interferometric localisation of the burst, which indicates that
the burst was detected in the primary beam of the Parkes/Murriyang 20-cm
multibeam receiver. We develop a Bayesian Stokes-Q, U, and V fit method to
model the GFR effect, which is independent of the total polarised flux
parameter. Using the GFR model we show that the rotation measure (RM) estimated
is two orders of magnitude smaller and opposite sign ($\sim$28 rad$\,$m$^{-2}$)
than the previously reported value. We interpret the implication of the
circular polarisation on its local magnetic environment and reinterpret its
long-term temporal evolution in RM.
