There were some problems with the early issued Cyclones relative to string breakage. Apparently (some) of the strings made by a subcontractor had fewer than required strand count.(This, from personal experience).Those problems were solved some time ago. But the hasn't catch up with reality. I'm on 4 crossbow forums regularly and have not heard of string breakage problems as of late.
But as bows get faster (speed sells) the potential for string breakdown increases. One has to be very vigilante for string wear and replace strings and cables that have been weakened immediately. Preventive maintenance is key to long C bow life, much the same as with any other high-performance mechanical object..