Zgemma h2s flashing picture

[pt1970]

Hello,
I have had a few of these boxes and set them up for friends but one of them is puzzling me.
It boots up fine , and everything works as normal until watching a premium channel when picture starts to flash large blocks of colour overlaying the program you're trying to watch which makes it unwatchable.
When you change to any fta channel ,the picture is fine as are all the graphics( menus/info bar etc.)
Maybe a tuner fault?
Anyone with any suggestions much appreciated
Thanks

[martin035]

If FTA channels/menus are OK I don't think it could be the tuners, I would try another different image or build your own image and install the relevant plugins and see if that makes a difference