So, the engineer came today (really nice guy), and he swapped out the connection point for me, as well as a length of extension cable that was running to it from the outside. He tested the connection (he had some really cool kit with him) and verified that everything was good up until my connection point.
So far the connection has not been noticeably unstable (and the Connectbox itself hasn't crashed) but I think I'll need to monitor it for longer.
I still see tiny amounts of packet loss (less than 5% generally, but up to > 60%, see attached images) but seeing that it doesn't occur consistently (in terms of time or amount of packets) across all the domains I am running SmokePing against, suggests to me that this is more likely a downstream issue (congestion or something similar) as opposed to issues with my connection specifically.
Here is also an example mtr output:
which does seem to imply congestion or some other problem, at least from the second hop onwards when pinging zoom.us.
I do see that the connection status reported from the Connectbox does mention uncorrectable errors (screenshot also attached), but given the engineer gave my connection a clean bill of health, is this is anything worth monitoring or complaining about? It is hard to find useful advice on this kind of thing without ending up deep into DOCSIS 3.1 documentation from equipment manufacturers - which is way outside my area of expertise - so I'd appreciate the expert take 🙂