You are not mentioning what model of device you are talking about (xpl3000, E1, E2, X5, U5, etc..) ? BuzzTV 5 is the App that is used on the newer devices.
What version of app is the box using ? From Live TV, if you press the menu button, it should be listed on the bottom of the menu. OR better yet, go to the "updates" screen from the home screen, and it should give you both the Firmware version, and the BuzzTV app version.
when you say "hard reboot" can you please explain what exactly do you mean ? Just unplugging and plugging the box ? Doing a Full factory reset ?
Are you using the integrated BuzzTV app, or using some other 3rd party app (smarters, stbemu, tivimate, etc..) ?
Have you tried switching video players (from LiveTV press menu, settings->Configuration and it should be on the top) ? Maybe his specific IPTV provider has changed something in some of the IPTV stream encodings recently which is not playing well with the video players.