Can’t solve TV freezing

Hi all. I’m at a loss. My one TV has been freezing (with scrambled picture) for a half second about every 30 or so seconds. After the online tech did a bunch of stuff on the back end and also got me to do a bunch of reboot techniques he said I need a new digital box. So here we are - new box, full strength wifi signal (fibre) new HDMI cable and it’s still pausing when watching tv. For the record - streaming service work fine. I’ve once again reset my modem, unplugged tv box and still does the exact same thing. Any ideas ? Our second tv is fine for the record.