@HB73 Trying hard to take this all step by step, especially when you have had 3 Hubs sent and two DVA's..... And that is why i asked all those specific questions, so here is what my experience was with that particular EE hub you have......
1. I moved from sky to EE, the sky hub had been on for years with zero problems at all..... As soon as i put the EE SH31B version on the connection at that time it was a FTTC old copper with speeds that sky had 40Mb/s down and 10Mb/s up, the hub was fine in operation so no real wifi problems etc but the sync speed to the Hub on the connection was just so poor.....
I had numerous visit's both EE Engineers and OR Open Reach engineers, just a lot off faffing about so going to say the first six were just not at it, the seventh i joked with the Engineer when he said it all looks ok, i said see someone in two weeks, that prompted him wait let me take my tester and have a good look, there was loads and loads off error's on the line......
It took him a good few hours back tracing the connection lift and check, eventually where the cable entered the home there was a GPO junction box, he lifted the tails off, crimped them to the cable that went to the Master socket instead off the old screwed GPO connection, ZERO errors now on the tester and from that day on not one single error at all ever.....
I knew the EE hub was good just because off the way it was working so did not have to go down the swap it out to see scenario..... All the Internal wiring was fine as it was all disconnected by ME (Multiple Extension socket's for landline etc), well before the checks all the Engineers had made,,, so it gets very hard to say the EE hub just did not like the connection in the slightest.
