An inhomogeneous wave exponentially decaying in all directions may exist near the edge of a circular aperture if the mass and the moment of inertia are appropriately chosen (i.e., their values coincide with the critical ones). In this case, the solution to the diffraction problem is not unique. This paper inquires into the feasibility of the solution to the wave diffraction and radiation problem in the case of critical loading. The solution is constructed according to the procedure suggested in [2]. It is shown that the diffraction problem always has a solution while the radiation problem may have no solution. The effects related to the critical mass and the critical moment of inertia do not manifest themselves in the far field.