Does anyone know of a simple option to graph the CRC errors and errored seconds on a 2820n ADSL line? (3.3.7.3_232201)

DLM has been knocking my line speed down but I suspect the problem is very intermittent bursts of errors from unknown noise source which affect line no matter if I'm on 6dB or 15dB.

I've asked Talktalk to turn DLM off, I now want to graph CRC count vs errored seconds to show how the errors affect overall line. Tried
-routertools- nothing relevant captured
PRTG- only does 1 min poll in free version
routerstats- can't seem to get it set right for 2820n- it will only give me the main stats page, not the WAN phy one which has the CRC counter.

There is a CRC block length in the ADSL MIB but I suspect this is not the CRC count displayed on the Draytek web page, I also don't think there's an errored seconds counter on the Draytek although I can probably just use a ping to tell me this.

Thanks!

Chris