Freeview probs.

I have an external 'digital' aerial and CT100 coax, as recommended by
a local aerial shop, and a 'booster' behind the telly.

(Bit peeved as the local aerial shop said all I'd need was the aerial
and coax but found I also needed the booster to get any sort of
picture.)

My freeview box (A Setpal) reports data quality as being almost 100%
most of the time but signal strength and signal quality are both
around 70%. All levels fluctuate +/-5% ish.

Most of the time everything is fine but every hour or so we get a
temporary picture lock up/sound glitch.

Any suggestions as to the cause/solution? More powerful booster?
ferrites? Bigger aerial?

sponix
.