LG 47LA860W - HD freeview tuner - video repeats/speeds up

Hi there, first time poster

I have just purchased a new 2013 LG smart TV, the 47LA860W. Ive had it for a few days now and im experiencing a problem that is seemingly with the in-built HD freeview tuner. Sporadically and every few minutes, the video will throw a bit of a spasm by repeating an already played video section from 3 or so seconds ago while the audio carries on absolutely fine then the video will go super fast (like it is fast forwarding) to catch up to a point where the audio is, then it will all be fine (until it happens again)

I do not get the issue with any of the SD channels

Just to add some clarity, My set up is very simple, I am taking a standard UK coax arial connection directly into the TV and thats it, no additional boxes involved

I still have my 4 year old Samsung 40" tv with built-in HD freeview tuner and when connecting up to the same connection I do not get this issue ..

Is there something I need to do to calibrate the HD tuner or something or is there something I am missing here ?.. I have upgraded to the latest available software update

Any help or advice on this would be greatly appreciated