If I remember correctly, you have a combined modem/router.
My advice is for you to power off the modem/router and leave it off for 30 minutes. During the 30 minute power off period, perform a quiet line test (call 17070 and take the relevant option). Once the 30 minutes have passed, power on the modem/router and keep watch (make written notes) of the LEDs activity following the power on.