Have you tried rebooting the box, if that hasn't worked you could try a factory reset of the box
It's only a partial system reset and not a complete factory reset. You are given 2 options,
Keep Recordings
Format Disk
Choosing Keep Recordings, means you won't lose your recordings and any planned recordings or series links you've set up, but you will have to sign into your apps such as iPlayer, Prime, Netflix and ITVX again, also Match frame rate and Standby power consumption will go back to their default settings if you have changed them.
If that doesn't work you might need the box replacing.
