I've just been out to Barrow Hill Junction, my railway to have an operating session and one of my Hornby Class 31s (bought from Olivias as D5806 with sound etc. has done a very similar thing.
I thought maybe somebody had dropped it, but the front of the body has fractured in just this way.
Obviously the model was probably manufactured some years ago and it seems the "good" Hornby Class 31 is no longer available, only the RailRoad Range one seems to be produced now.
It's a real shame as it ran well, sounded great and looked superb, but now it has a big crack in it.