  We calculate quantum loop corrections to the stress-energy flux caused by
moving mirrors. We consider massless, self-interacting, $\phi^4$, real scalar
theory. In these calculations we encounter a new and quite unexpected
subtleties due to the absence of global hyperbolicity in the presence of
mirrors. We attempt to clearly phrase as many as possible hidden assumptions
and complications that appear along the course of the solution of the problem
in question. On top of that we find that quantum loop corrections to the
stress-energy flux are growing with time and are not suppressed in comparison
with the semi-classical contributions. Thus, we observe the break down of the
perturbation theory, discuss its physical origin and ways to deal with such a
situation. As a byproduct we observe a similarity of the problem in question
with that for the minimally coupled, massless scalar field in de Sitter space.
