[Sephiroth]

When I had discrepant stats some months ago, the PT arranged for the cabinet amplifier to be replaced. They are supposed to be "sloped" so as to provide correct downstream power for the frequency range (attenuation is greater per metre for higher frequencies). The upstream power requirement is set by the remote CMTS based on what it needs to set in order to make sense of the data received. In dire circumstances, power rises to the maximum (58 dBmv) and the TBB would then show considerable packet loss. The upstream impairment can be anywhere between you and the first active node (the optical node). Most non-interference upstream impairments in the bit between the home and the cabinet have downstream consequences to (like low power and sometimes poor SNR). You don't have that. So it's likely to be between your tap point and the optical node. But, as I've said before, your neighbours would have that problem too.

You should, if you can, research your neighbours' experience. The fact that you have a PT's attention should be siufficient to get this cleared up.