Unfortunately the big radials tend to have quite a few failures of various kinds, especially these days when there's not that many of them around so the in-depth maintenance knowledge is harder to come by.
Reliability for day after day trouble-free (or at least not much trouble) operation would have to be a major factor in running a business like that, I wouldn't like the sleepless nights wondering when the next unscheduled maintenance was going to be needed - not saying that's what may or may not be the case here, but in my experience your chances of doing a day's flying as planned with that kind of engine are quite a bit slimmer than with more modern kinds, sadly.