I have been working around these engines as a LAME for over 30 years and have to admit I am someone perplexed at some of the replies. I guess probably a reflection of what we also see on other threads, a little gossip, some rumour but not always too much fact.
I was a little surprised to see a previous post about barrels failing about the hold-down studs. A new one on me, I know Norton Commandos used to crack in that area.
As for cylinder failures......of course aircraft engines pop cylinders... what do you think the engineers are doing checking around the head and attachment area during their inspections.
On some engines I can name it is probably more common than the other failures like piston, ring or valve related.
In my experience of engine failures most have been caused by incorrect handling, either directly or indirectly.
A full failure is most often fuel related, very little redundancy and plenty of potential for failure modes. I guess the same could be said of the lubrication system but that generally gives at least a little warning.
Partial failures such as valve issues, or popping the head, I feel are caused by poor handling, incorrect heating and cooling etc. Guys trying to burn plugs off to improve a mag drop etc.
A cylinder head failure is nasty, but not the end of the world. Sure there will be a decrease in power.. and some oil spray. But it is leaking from the pushrod tubes and the engine can continue running for some time. The exhaust and intake manifolds ensure the cylinder head is still held close to it's original position.
Many pilots used to declare a failure and shut the engine down, - now you do have a full failure.... and the risks to the aircraft.
I am sure many here have experienced a cylinder popping and have stories to tell. Hopefully a pleasant ending.