Spurious polarisation in spw 3 (solid lines) for five representative Monte Carlo simulations. The spectra are extracted at the position of the line peak. The quantities are given in Jy. The short dashed line indicates a total intensity spectrum (not to scale) for illustration. The long-dashed lines are the observed Q, U, and V polarisations at the same scale as the simulated spurious polarisation spectra. It is clear that the magnitude and spectral behaviour of the observed spectra is significantly different from the spurious signal.