I am/was having the exact same issue. For me it was the CRC errors were incrementing. What I found was that just before the DSL dropped the SNR downstream would drop to below 2dB.
I also had a line tech come out and he cleaned up the lines and increased my DSL speed. He saw no errors on the line.
I also found that if I unplugged my C1000A the problem would go away for a time. The longer it ran the more frequent the DSL dropping became to a point.
I searched around and could not find a good post about this and so I figured I better replace the modem and see what happens. I just installed the very same modem C1000A. The first thing I noticed is that my downstream SNR was 14db. On my old modem the best I saw was 9db. The new modem has been installed for about 1hr and so far no CRC errors and my SNR is between 12 and 14db.
I am pretty convinced that this is an issue with the ActionTec C1000A. I looked for updated firmware but I was running the latest. I would recommend giving them a call. It is possible they have a component issue.
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