The problem manifests on lines where the SNR changes up or down in succession. It can also occur on rare occasions where the SNR rises above 9 to 12dB. You will also see issues when there is excessive noise on the line. Most routers will adjust the sync accordingly, however the TI-AR7 chipset results in intermittent connection problems, aswell as No Sync and No Auth.
It is not a case of Saying that all ROUTERS are at fault. It is suggesting that with the current BT Infrastructure the AR7 chips can not cope with the excessive noise levels, and hence they manifest as an intermittent connection or No Sync and in some cases Auth faults.