  Swift J1745-26 is an X-ray binary towards the Galactic Centre that was
detected when it went into outburst in September 2012. This source is thought
to be one of a growing number of sources that display "failed outbursts", in
which the self-absorbed radio jets of the transient source are never fully
quenched and the thermal emission from the geometrically-thin inner accretion
disk never fully dominates the X-ray flux. We present multifrequency data from
the Very Large Array, Australia Telescope Compact Array and Karoo Array
Telescope (KAT- 7) radio arrays, spanning the entire period of the outburst.
Our rich data set exposes radio emission that displays a high level of large
scale variability compared to the X-ray emission and deviations from the
standard radio--X-ray correlation that are indicative of an unstable jet and
confirm the outburst's transition from the canonical hard state to an
intermediate state. We also observe steepening of the spectral index and an
increase of the linear polarization to a large fraction (~50%) of the total
flux, as well as a rotation of the electric vector position angle. These are
consistent with a transformation from a self-absorbed compact jet to
optically-thin ejecta -- the first time such a discrete ejection has been
observed in a failed outburst -- and may imply a complex magnetic field
geometry.
