VLC freezes during IPTV recording

[Joejim]

I use Win 7 on PC.
I have m3u8 file(live tv channel streams) from my IPTV service that I feed into VLC to record. Often overnight.
When I wake in the morning, sometimes VLC is picture is frozen and VLC can't be closed. I have to open task manager and end process manually to close VLC.

What is causing this?
Is it because live tv stream is buffering/pausing? But it should only stop IPTV feed thus frozen picture shown, but not lock up VLC program in Windows.

Also can I set buffer cache in VLC for live streams? I think cache buffer settings only effect VOD(re-recorded tv shows/movies) but not LIVE streams like live sporting event. So cache setting in VLC is useless for live tv streams?