Comparison between old and new QPE phases. Upper panel: Typical model light curve for observations during the old regular QPE phase. Lower panel: Qualitative representation of the light curve from the XMM12 observation (new QPE phase; solid line) and one possible extrapolation of longer-term behaviour based on the arguments discussed in Sect. 3 and Appendix A (dashed line). The light curves were normalised so that the intensity of the strong QPEs is the same in both panels. The same quiescent level is assumed for visual clarity.