Computations are reported of the plasma-sheath in electronegative plasmas at low pressure using the fluid model in the parameter region in terms of negative ion density/electron density and electron temperature/negative ion temperature where oscillations in potential, electric field and charged particle density were previously found. In this paper, in contrast, the positive ion temperature has not been arbitrarily set to zero but has been allowed to vary, to become comparable to the negative ion temperature. It is concluded that the oscillations arise from the unphysical assumption of a significant difference between the ion temperatures, which suppressed positive ion diffusion as a mechanism to smooth out density variations. Thus, the oscillations are not intrinsic to the fluid model but rather they arise from arbitrarily setting the positive ion temperature T_p = 0.