Beam control under thermal blooming conditions based on phase conjugation and phase-conjugate reflection algorithms is considered. The stability of these two methods for correction of nonlinear distortions is analyzed. Instability of phase conjugation is shown to be due to violation of the optical reciprocity principle. Rigorous fulfillment of this principle allows achieving the stable correction. The phase-conjugate reflection in nonlinear medium is also accompanied by violation of this principle, and this leads to development of oscillations in parameters of the light field on a focusing object.