Unfortunately that isn't the case for us, as we were moved from a Hub 3 to a Hub 4, and we've still got the issue, and we use a Panasonic cordless handset (single unit).
Our issue only started when we were put on the faster bandwidth, from the VM100.
I could only then put it down to the change in speeds or something to do with the port scanning on higher bandwidths.
Regardless, VM haven't been back in touch about my wife's lost revenue, and are happy to have closed our issue as fixed, and so the phone is unplugged and this we're paying line rental for no purpose whatsoever due to the service being better when it is disconnected