Not a failure I've seen before. I always turn off the cylinder as soon as I'm done - not that I would have considered a hose blowing, but the hoses do degrade and the o rings on the end that seal the fitting into the bottle don't last long so can have a tendency to leak. It's more about saving the gas so I have some for the next BBQ and it not all just drifting slowly away rather than safety though - but I do always check the hoses, connections and fittings regularly as well. Between the 2 BBQ's at home, the homemade spit and the Ziggy in the Motorhome, I seem to end up buying a new hose once every couple of years anyway as they degrade and start to crack - cheap and easy fix.
How old is it? According to their website, the hose should be covered for 2 years -
Warranties | Napoleon - I would consider the hose to be part of 'All other parts' - so it shouldn't cost a cent to fix.
Edit - just looking at some user reviews of this grill and most are favorable, but the ones who weren't seem to have issues with the gas line, fittings and controls - so maybe not an isolated incident with them, but it does seem that they back their warranty so I'd be giving them a call.