I'm not sure it's a 'traction package' update, the issue with stabled 331s/397s was apparently caused by the auxiliary converters rather than the traction converters. A memo was posted dated 5th Dec staying that a software update had been successful and the instructions for dropping the pan when stabling within the triangle around Preston/Blackpool no longer applied.Roger Ford now reports the problems have been resolved with a traction package software update.
The regenerative brake is still to be isolated on the 331s (I've no idea on the 397s).