Top 1cm screen unresponsive

[pete_P38]

This week the top of my touch screen became unresponsive.

So far I have tried the following:

1) Unplugged & re-plugged the 100cm screen cable at both ends.
2) Power cycled the stereo.
3) Tried various apps, but all have same issue with top 1cm touch area.

Any ideas ?  
Is there a touch calibration somewhere ?

Thanks,
Pete