I might get in trouble for saying this , but a couple years ago I had the misfortune to be stuck behind a TW connection, they systematically and consistently delayed my rtp traffic every few minutes for 30 seconds or so. I explicitly documented such behavior to their technical support but they denied it was happening. I stopped using them, and they were eventually and I believed successfully sued for doing that.
You can set rtp debug on and watch the traffic stream , if the timestamps and the interlacing are not close to perfect then perhaps suspect the same bad habits have returned.