Measured timing residuals from timing solutions fitted by the unbinned likelihood maximisation method. (a) Residuals between the best-fit timing solution given in Table 1 over the data span. (b) The same as (a) but around the epoch of the first glitch event (blue line) in comparison with residuals between the pre-glitch model (green line). (c) The same as (a) but for the sixth glitch event. The shaded region corresponds to statistical uncertainties.