We then had an antenna guy turn up and he installed a booster.
He showed me that the signal was too weak, but after the booster as installed, it was more than adequate (I forgot the number that it had to be).
I do still have issues with the signal on some channels, but seems like it’s only around 6-7pm.
What can it be?
It comes and goes. Absolutely fine for a few mins, then a period of weak signal for 15-20 secs and then back to normal again for a few mins.
Video of the issue below: