Zoom-in on the light-curve evolution during the last four years of the ZTF coverage. WISE/NEOWISE W1 filter: brown crosses. ZTF r filter: open orange circles, g filter: open blue squares. Black arrows mark sudden brightening events. The grey arrow indicates the date of our spectroscopic observations. Observations in some filters were offset by a constant value for clarity, as indicated in the plot by a number in magnitudes.