I have found that if you go into the settings for each tuner, on Tuner Type you have to switch to the unused service and change the configuration settings to 'nothing connected'.
It will then scan as normal.
I'm not sure if this is how it's supposed to be? You don't need to do this on ViX.
It will then scan as normal.
I'm not sure if this is how it's supposed to be? You don't need to do this on ViX.