This often happens when some water is trapped in the cartridge and freezes after a cold snap. It expands and cracks the ceramic disc inside. An expensive lesson I learned after my first winter when the shower one split and wasn't covered bt warranty. Best to leave the taps on the open position this time of year.
Dave.
------------- Never argue with an idiot, they will drag you down to their level and beat you on experience.
Mark Twain.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.