You could try a factory reset.
Go to Settings > System > Factory Reset
You are given 2 options, select the keep recordings option,
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 ITV X again, also Match frame rate and Standby power consumption will go back to their default settings if you have changed them.