Example of the ‘stippling’ effect as previously described in Czekala et al. (2021). The top panel shows nine channels of a zoomed-in region in a restored image cube, cleaned using a 3σ threshold. The central channel shows the resulting spurious emission peak. This bright emission, of order the beam size, is only present in a single channel, while the neighbouring pixels show no equivalent emission. The bottom panel shows the model extracted at the central pixel, where the bright model component (green line) is only found in a single pixel and channel. This model component is then convolved with the Gaussian clean beam during the tclean run to produce the restored image, resulting in spurious compact emission in a single channel.