Pulsars usually "pulse" very rapidly and in very short bursts[0]. This one pulses only once every 18 minutes, but in bursts that seem to last for a minute. Some articles mention the possibility of a star-quake which as I _think_ could be caused by either further decay of the magnetar, or the magnetar absorbing more mass

[0] - https://www.sciencedirect.com/topics/physics-and-astronomy/r....