When I was talking to the dealer parts guy last week,he told me,that they have seen quite a few burst,although he didn’t put a number on it.
He also said that they had two cars come in from independent garages,that had the bag burst and the independent changed the heater matrix but,after that they couldn’t get all the silicate flushed out of the system.They had to book it in to the main dealer as,they have a machine specifically for flushing the system out.they hook it up to this and it goes through a process of flushing back flushing.
It does this for a preset time,then all is ok.
As my car is now four years old I decided to remove it.