Hello,
This is my post but I made DCPs for several years, fisrt ones "by hand", then OpenDCP, and now DCP-o-matic.
I had an issue last week and irt was that I made a DCP out of an Apple Prores file, adding subtitles, and in my demo copy of easyDCP Player it played well but the client said that when trying it at the cinema first seconds were OK and then black screen, subtitles and audio ok, but black screen.
I was using the last version of DCP-o-matic so I went to the last "stable" one, went to my Avid suite and converted the prores to TIFF stills and redid the whole project again and now it's fine so I can say if it was the las version of the software or the proress (under Windows) conversion, just for you to know.