I think there are known faults with the optical link from the cabinet to the exchange.
A few of my neighbours on FTTC with Sky,BT and Zen have all been experiencing severe packet loss over the last two weeks and the common factor is the connection/equipment from the cabinet to the exchange. Sync speeds are perfect so VDSL is not the issue. Seems to be upstream packet loss. Speed tests show very poor upload speeds as most packets are being dropped. Speed Test
BT support don't believe there is an issue as they can't 'see' a problem, they don't have the means to test anything other than download speeds and blamed the poor upload on the speed test being variable. They even told a neighbour it was noise on his line and would go away...useless
Zen confirmed there is a packet loss issue and have been working with Openreach to get it resolved. (good reason to leave BT for Zen) Unfortunately it's taking a while and we are still suffering after two weeks.
I think that there are known faults with the Huawei MA5616T DSLAM (link to cabinet info)
used in the cabinet or another common component such as the optical uplink to the exchange as there seem to be others with the same packet loss issues on the forums. A faulty optical card at either end could affect just the uplink and cause severe packet loss for everyone on the same cabinet. Pingplotter shows packet loss at the first IP hop the same as you found adtyne.
What cabinet are you connected to? Is it the same MA5616T DSLAM?