**This is just for fun / speculation as the issue is under investigation by Enhanced Support / OpenReach / BT Wholesale**
Two sites on Zen and BT, FTTC, IPs 88.97.13.173 & 81.133.250.29, sites are about 150 meters apart. Both have suffered 5-20% packet loss for around 6 weeks. Copper status and VDSL statistics are great, great speeds, no drops, few errors etc. Many many Pair Quality Tests have been conducted 😉
Logging shows a very noticeable improvement in packet loss in the wee small hours (daily):
Lift and shift has been carried out for want of a better idea.
Running traceroute and pathping, the loss appears to occur on the last hop to the premises - ie from outside you can ping all the hops except the fault premises without loss
Engineers have also ruled out CPE, hot VP, electrical interference (REIN, SHINE).
I've now got a fiver on 'broken BRAS', but I know diddly squat about VDSL delivery, so would love to hear other wild guesses. Have at it!
I'd like to compare mine. Will post it tomorrow. Is your IPv6 connection as bad?