Although falling under the neglect catagory , frost cracking and running out of oil have to be on the list !!! Then I'd put a stake on valve gear related issues.
Not really.
The CS was never a continuous duty engine, standalone or start-o-matic, and it wasn't built for continuous duty, however.....
Directly I can tell you about anything from one or two CS's at a time to at one point just over 50 of them, indirectly the highest number has to be old peter who is long dead now, but who was responsible for over 500 units in iran.
They didn't actually have a failure mode, provided they were routinely inspected and serviced as required, where do you think the 100k hours plus stories come from.
With wilful neglect I've seen actual sweet examples go to scrap in a week, on the other hand I've also seen CS's run hundreds of hours with cracks right across the piston, with lube oil that was at least 50% rainwater and with the slimy consistency to make webs between your fingers, injectors that basically didn't atomise any better than my shower, you name it.
I know for a fact that we had one 6/1 in particular that used to run for 9 days solid, then stop for a maximum of 3 hours, and a minimum of 1 hour, before going again. I know that because it was running a brine pump and it was plumbed into a 45 gallon drum (of diesel), when it emptied it the drum was changed, and the guy doing the rounds did them every 3 hours. That engine was clocking up over 8.500 hours a year, and apart from routine service, plus routine head and injector service every 2.500 hours, nothing ever went wrong with it.
My s-o-m stands out in the garden, it isn't covered in any way, sometimes it doesn't run for 3 or more months, but it never fails to start and instantly settle down to a sweet steam engine beat, only starts to thump if you out some load on it.
My stock of lister spares for it, and the old lister D, is precisely zero. Just not needed.