Maxima and minima of the profile-shape differences shown in Fig. 3. Error bars indicate 2.88 times the off-pulse RMS (since for Gaussian noise there is a 1/256 chance of a measurement falling more than 2.88σ away from the mean of the distribution and the pulse profile differences considered here consist of 256 bins). The profile-shape distortion due to scattering is clearly visible before MJD 57000 with a residual amplitude that decays linearly in time. Between MJDs 57000 and 57600 the profile differences are not fully consistent with Gaussian noise, but are stable. After MJD 57600 some further, lower-level, variations occur.