I have TPLINK W9980 with OpenWrt with FTTC 100/20 connection with 17a profile (SNR 6 dB upload 6 dB download). If I tweak SNR in download, for example -2.0 db, when dsl line is connected the SNR change to 6.0 to 4.0 dB and dsl connection get faster. But after 1-2 minutes the SNR return to 6.0 db and consequently dsl connection slow down. I think that it is caused by SRA or DLA but can't understand how to disable them. What can I do?