That's too much of a simplification. There are 2 ranges, one for a clean line, one for an impacted line. Currently the line is in the impacted range. An engineer visit is required to discover why.

The first engineer had a stab at the reason but was absolutely incorrect, laughably so.

While a simplification, it needs to be highlighted to the poster that getting another engineer out does not ensure any guarantees of an uplift and this may well just be cross talk or the checker being over optimistic (don't take the Openreach figures as gospel)

It could be problems with the new Smart hub. I've seen reports that it has issues.

We need to stop bashing the smart hub. Yes it has a couple of issues but certainly can achieve a full sync on a good line. By no means would it shave off 30Mbps.

There were a few faulty ones but the stats here are not characteristic of that particular fault.

I'm aware of reports of a fault where is refuses to go above 10mbps upstream, which seems similar if not exactly the same. Are you?