On the first day of a new connection (estimate 67-80 - around 350m from cabinet) last week the sync was in the high 70s. First problem was getting the PN profile reset. Then variable throughput in the evening period as others have mentioned - I raised a ticket and some tests were run and that issue seems sorted. Meanwhile the sync had dropped 10% during the first few days which didn't seem too bad
I was probably the first FTTC connection on this cabinet and today I noticed someone else being connected, but tonight to keep the 6dB margin I'm now synching at 66 - I'm really surprised after just a week I've fallen below the estimate range.
