could be a sign of networking issues.
Are you watching ytubes online, or any sorta videos online thru another device (PC) at the same time ?
Is anyone gaming on your network ?
Does your high speed LAN line have a filter system ? (if this is an issue, you would know it if the telephone rings and at same time IPTV freezes).
What about Hardwired (cat5e or cat6) cable ?
Or is it working thru wifi ?
