Video in linked article did not work. Here's the official version:
Actually, according to Northrup Grumman it wasn't nearly as bad as the OP's failure. They claim "the test was successful, the motor performed nominally, the observed behavior of the aft exit cone of the nozzle will be investigated." No holes were burned in the side of the motor. It looked very dramatic and it clearly affected the thrust plume, but the booster motor survived intact. Almost like a spit liner.
Tony