Caustic and other high pH fluids attack some ceramics and silicon carbides. Cracked or broken. The product is solidifying between the faces.
Most hard faces have poor tensile or shear strength.
Excessive vibration will cause cracking at the drive lug location. A cryogenic fluid is freezing a lubricant that was put on the face. The elastomer is swelling up under an outside seal face. This problem can also occur if the seal design allows a spring to contact the inside diameter of the hard face. The shaft is hitting the stationary face or the rotating seal face is hitting a stationary object.