Connection issue plausible but odd though it only affects Bbc.

Or try, Check transmitter faults | Help receiving TV and radio in case its a localised fault

Only other thing I can think of that could cause it apart from faulty tuner is the aerial has moved, that will cause variation in signal and the weakest tuner will not pick up the signal as not all transmitters send out strong signals all the time, and as yours is split could weaken it enough to prevent you getting it on that tv I would check the aerial alignment just in case its moved

even a bad attenuator if fitted could cause it

Maybe, but normally the main BBC channels should be the strongest signal. I agree with Brit in Germany that a quick rescan of the channels is a worthwhile and easy first step before mucking around with swapping TVs around or fiddling with the aerial or its coax cable connection.

Channels do occasionally get changed in the frequency to accommodate new channels or, in some cases, to allow for some frequencies to be used by 4G+ mobile phones.

Just a thought. Is the Non smart TV analogue? And the smart ones digital? Maybe your local BBc signal has only just gone digital only. Probably not the case...just a guess.

They all finished changing from analogue to digital by around 2012. All the analogue TV signals were never transmitted again in the UK.

One problem could be that its one multiplex of frequencies (also called 'mux') that might not be transmitting due to some issue at the transmitter, or something is specifically interfering with that range of frequencies.

Below is a link to the current list of channels and the mux they belong on, per region:

www.freeview.co.uk/corporate/platform-management/c...s

As some Freeview channels do change their number, they may change frequency and maybe mux as well from where it used to be. For some reason, when that sort of thing happened where I live (western edge of East Anglia), some channels worked for about a week after the change without re-scanning, then dropped out, requiring that to be done for them to return in their 'new home' (channel number).

Note also that there is a useful 'work-around' for those of us using DTV PVRs to record TV shows and films to be able to record two programmes and watch a third live, for recorders with two tuners:

Essentially two of the three programmes need to be on the same 'mux', plus there is no time overlap between existing programmes being recorded and subsequent ones.

Some PVRs have a feature to 'pad' programmes at the start and/or end by X minutes to avoid them starting late/finishing early if left to its own devices (they sometimes get it wrong), but then this 'overlap' problem kicks in and can cause its own set of problems, because it forces you to choose as it happens.

No good if you're not there - the software either chooses for you, and can cut off the end of a late-running programme to 'start' a recording still on adverts, or the machine chucks a software wobbly, and depending upon the situation, may lose at least one of the recordings entirely (not starting one or corrupting it so it cannot be viewed) or losing several minutes of recording time whilst it reboots the system.

Essentially like the old 'Windows blue screen of death' but right at the crucial part of a TV show or film you don't want to miss!

Also useful to update your PVR / TVs operating system software if a new version is available, especially if it includes patches to fix problems (e.g. the above, system hangs) or to get new/improved apps on 'smart' ones.

The downside can be if that upgrade removes apps that the manufacturer no longer has an agreement to use any more. Always check before doing this, and if possible, download the update onto your home computer/tablet and then onto a USB stick (if the TV/PVR has the ability to update via one) as it is less time-consuming that doing so 'over the airwaves' and if it fails, you can instantly try it again, or to update an identical unit, saving time.