  We study the dynamical properties of point-like defects, represented by
monoatomic chalcogen vacancies, in WS$_2$-graphene and MoS$_2$-graphene
heterobilayers. Employing a multidisciplinary approach based on the combination
of ab initio, model Hamiltonian and density matrix techniques, we propose a
minimal interacting model that allows for the calculation of electronic
transition times associated to population and depopulation of the vacancy by an
additional electron. We obtain the "coarse-grained" semiclassical dynamics by
means of a master equation approach and discuss the potential role of virtual
charge fluctuations in the internal dynamics of impurity quasi-degenerate
states. The interplay between the symmetry of the lattice and the spin degree
of freedom through the spin-orbit interaction and its impact on charge
quenching is studied in detail.
