I'm just adding my voice to this issue.
Address 1: We have BT infinity with a home hub 2 + openreach modem.
Address 2: we get BT infinity with a engineer fitted home hub 5.
Address 2 the broadband keeps dropping, we contact support, do numerous test, they send a replacement homehub.
one of the recommendations the woman in support gave us was to try disconnecting everything else (single phone) from the line.. as we dont use the phone it's not a problem... This does fix the issue (although please note we have had the same phone for much longer than we have had broadband issues).
As this "fixed the issue" when the replacement homehub 5 arrived I didn't swap it over.
Address 1: never an problems, just 2 boxes, 2 sets of power points is all untidy, so I replace the lot with the new home hub 5.
Now the broadband keeps dropping... but here the phone is used and cant be removed.
I'm aware a quick fix solution is to put the old equipment back.
I'm really just adding my voice to the concerns that home hub 5 is borked!
edit: fyi: by "line drops" I mean broadband stops, and hub orange light comes on... exactly the same issue both addresses.. most deffinately different exchanges.