We have observed a rapid decrease in the lifetime of a homogeneously precessing domain in ³He-B at a temperature of 0.4T_c. This phenomenon does not depend on pressure, magnetic field, or on the presence of ⁴He covering the surface of the chamber. We suppose this effect is the result of a magnetic relaxation through some unknown channel. Catastrophic relaxation may possibly be connected to some new phase transition in ³He.