On the non-constancy of speed of light in vacuum for different Galilean reference systems

It is established that when two inertial frames are considered, one of which is attached to a simple dissipative medium at rest, and the other to a perfect electric conductor in uniform rectilinear motion with respect to the first medium, the speeds of light in vacuum in the two Galilean reference frames must necessarily be different in order for Maxwell's equations and boundary conditions to be able to account for the loss in the first medium. This results negates the Special Theory of Relativity which postulates that speed of light in vacuum for all Galilean systems is constant.