  Context: Class II methanol masers at 6.7 GHz originate close to high-mass
young stellar objects (HMYSOs). Their high sensitivity to local condition
variations makes them a useful marker of the activity of the emerging massive
stars. Aims: We aim to closely examine the variability of the 6.7 GHz methanol
masers in Cep A HW2 using the new and archival single-dish and high-resolution
Very-Long-Baseline Interferometry (VLBI) datasets. Methods: We monitored 6.7
GHz methanol masers towards the target between 2009 and 2021 using the Torun 32
m radio telescope, and analysed nine datasets of VLBI observations taken over
16 yr. Results: Faint, extremely redshifted maser emission located close to the
presumed central star position and coincident with the radio jet shows flaring
activity with a period of ~ 5 yr. Flares have an asymmetric profile with a
rise-to-decay time ratio of 0.18 and relative amplitude higher than 10. The
velocity of the flaring cloudlets drifts at a rate of 3-4 * 10^-5 km/s/d for
about 11.5 yr of the monitoring. The time-lag between the peaks of the two
flaring features implies a propagation speed of the exciting factor of ~ 1000
km/s. Synchronised and anticorrelated variations of the flux density of blue-
and redshifted features begin ~ 2.5 yr after flares of the extremely redshifted
emission.
