Caravan tv problems

Hi all, perhaps i am not quite in the right section but the forum website is having problems too i think and will not let me post where i wanted to.

i just wanted to ask if anyone else has had problems with the grade uk vision plus tvs.

My parents and i bought one each in 2010 but have had nothing but trouble with the picture breaking up randomly and the tv listings being all wrong and out of sinc.

We have upgraded all the aerials and fitted a booster until we have gone as far as we can.

They have now gone back to the manufacturers who say they cannot find a problem.

The tvs work better when hooked up to a main aerial in the house but the picture just breaks up in the caravan, this can be after 10 mins or an hour but the signal bar stays the same at approx 51 %.

Also they have a very narrow field of vision, bit to the left or right and the picture goes negative.

we have swapped tvs too and they still do the same.

Also when hooked to a caravan aerial point  on a site they do the same.

Anyone else out there with the same problems?

I think  grade uk think i am making this up and blame the freeview suppliers for the out of sinc listings.

Would appreciate any info  or similar experiences...

Thanks