This has been happening to me, routinely, but with very specific files. I record off-air TV with my computer, using EyeTV software. Up until recently, it's been working like a charm - record the show, compress it and place it in my iTunes library and I can watch it with AppleTV or download it to my iPad when I travel. BUT - in the last few months, my AppleTV 4 will not play FOX TV files - just X Files and Gotham files. I get the 'Error Occurred...' message. Here's the weird thing - my AppleTV 3, on another TV, plays the files without a problem, as does my iPad when I load them onto it - but, if I try to Airplay the files in question - my AppleTV 4 won't play them. I get the spinning gear.
To me, this smacks of some kind of HDCP implemented by FoxTV and recognized by AppleTV...not a good sign for simple off-air recording.