I must admit, I still can't see why it needs to jump to ITV2+1 to record it though.
Let me try to explain. In place of the old system with five analogue TV services (BBC1, BBC2, ITV, Channel 4, Five) occupying one whole broadcast channel each, the digital terrestrial TV system broadcasts digital data on up to six channels, with the data on each individual channel able to carry 4 HiDef services or about a dozen StDef services, as well as a number of audio services and data services (teletext etc). We call each of these broadcast channels (carrying a specific set of services) a "multiplex" or "mux".
The HDR-FOX is equipped with two tuners, which means it can receive the data for up to two multiplexes at a time. If you are recording one service, then obviously that takes up one tuner and the second tuner is free to view any service from any multiplex as a live feed. If you are recording two services simultaneously from the same multiplex, again that only takes up one tuner and the second tuner is free to display any other service. If however the two recordings are from different multiplexes, that requires two tuners and the live feed can then only come from one of the other services on the current two multiplexes. The distribution of services across the multiplexes is listed
HERE (click).
If the HDR-FOX is about to start a recording and the two tuners are currently committed on another recording and the live feed, and the new recording requires a different multiplex, the new recording takes priority over live viewing and flashes up a message that it needs to change channel. If you choose to opt out the recording gets cancelled, but if you do not respond the channel gets changed (and you may lose the start of the recording in the period of grace). The HDR-FOX can only record two programmes simultaneously and view a third (as long as only two tuners are required), although it is possible to make a recording of the third channel by waiting for one of the existing recordings to finish, then wind back to the start of the live programme in the timeshift buffer and press record.
The HD-FOX only has one tuner, and can only record one service (when equipped with an external hard drive) and view another from the same multiplex.
I've never seen that happen before.
Then you've been lucky.
I wasn't actually watching BBC 1 when it jumped to ITV 2+1 but if I had been it would have spoilt the programme I was watching and I would have missed a bit.
You presumably have the HDR-FOX for the primary function of recording programmes to watch later. You know it is going to go off and "do its thing", so if you want to view live TV at the same time without interruption you should use the TV's antenna input instead of the HDMI feed from the Humax.