@Lord-Aries Local data over your network shouldn't count against your monthly data due it streaming from your pc to your chromecast on your LAN. Your internet could be turned off, but as long as your network was up you could still perform this. Hope this answers your question :-)
An addional thought: I spent 35 years in IT developing database applications and we would NEVER allow a situation where software does not work without putting out meaningful and accessible diagnostics. What a concept......
@stellychristy We know that the issue is on our end but what we're trying to do is track down what types of files are effected so that we can reproduce what's happening on our our computers, (and patch whatever it is)
I have precisely the same problem with my parents laptop but the playback is not smooth as presumably video stream requires substantially more CPU power than this laptop has available (Celeron B815 @ 1.6 ghz :s).
Ram usage doesn't appear to be a problem though. Some movie files work fine even though they are the same container (.mkv) but presumably use a different audio / video codec.
I have tested the same files on another TV and another chromecast with the same problem (brother has his own setup downstairs) but I dont have another pc to stream from (brother only uses it from his phone and his laptop is even worse than my parents)
Is there a format i can convert their movie files into which will assist with smoother playback?