Noise and interference on tv

[Joe+999]

When I switch the tv on, for about an hour, I get a screech for a bout 1 second, sometimes the picture goes black or the lower quarter is fuzzy, again only for about 1 second. I swapped the hdmi cable to a different port, I have swapped the hdmi cable but still it persisted. I unplugged sky from the tv , watching via an aerial and there is no fault, I believe the fault is with the sky q box. What can be done ?

[Chodley]

Was the new hdmi cable certified for 4k? It could be a faulty box but also looks like classic cable fault symptoms.