We consider the process by which a dislocation overcomes a double potential barrier in a thermally activated plastic deformation. We use the framework of reaction rates without taking into account the form of the barrier profile. In order to take into account the possible delay of the dislocation in the potential well we introduce the probability for overcoming the barrier with one jump and the probability for the dislocation to fall into the well. As a result we establish that the experimentally determined activation parameters of a plastic deformation not only depend significantly on the form of: the barrier, but also on the delay probability of the dislocation in the potential well, which in turn is determined by the mechanism by which the moving dislocation dissipates energy. Since the dissipation of energy by the dislocation and the delay of the dislocation in the well grow with temperature, it is possible to observe a temperature interval where the stress flow also grows with temperature.