@dan585 using google chrome, press the three little lines on the top right and sign in to your google account. Make sure you have the videostream extension installed on google chrome as well as the googlecast extension.
Thanks to Mourgie and others, i found the file that freezes videostream. Its 9GB .M4V movie :) .
If i try to launch him first, it's in status "loading" and if i'll not restart chrome, i can't stream any file.
@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......