Internet Routinely Spiking to 3000ms

I have had a repeated, ongoing problem with Xfinity where my internet regularly spikes from a resting 20-30ms to 3000ms every ~30 seconds. I have turned off the MOCA and turned off the "Stateful" setting. When I have previously reached out to Xfinity about this problem, they set me up with a new modum as opposed to solving the problem. The new modum fixes the problem for perhaps a month or two, before it returns. I am unable to speak to an actual person about this problem and it is incredibly frustrating for someone who works from home. Please advise.