Hi guys.
To clarify, the packet loss occurred on Stadia regardless of whether or not CRC errors / errored seconds were logged by the modem in the same time period.
Had another visit from 2 Openreach engineers earlier (I told my ISP about the packet loss, and asked them if they could do anything specifically at the exchange / FTTC cabinet). The engineers said the fault had been logged as 'low speed' when they turned up
Anyway, they told me that the line is aluminium and so the impression I got was that there isn't much they can do, regarding the packet loss (they also mentioned that my line was connected to a 'distribution point' shared by 10 other lines).
They offered to enable interleaving on the upstream part of the connection (one of them said he sometimes used to enable interleaving on ADSL connections to reduce packet loss), so I will see what difference this makes. Latency has increased by 19ms (now around 29ms to bbc.co.uk). So, hopefully that won't harm things too much.
Aluminium cables apparently aren't twisted, so I assume this means they are prone to noise / interference.
So, aluminium line on a ECI cabinet, only the best for us
. Apparently the best you can get out of an aluminium line in our street is 60mbps downstream (which admittedly, isn't that bad).