SB8200 modem causing interference on cable line for neighbors ?

I went to on vacation in Asia for a few weeks in late november. I started daily getting phone calls from Comcast about a line issue with my cable, and was told to setup an appointment ASAP, which of course I couldn't do since I wasn't home. When I came back, I noticed that my speeds had been cut in about half (500/20 from 930/40)

I finally had the Comcast tech come today. He said my modem was causing inteference and problems for neighbors. This was flagged by the network team, and Comcast put an attenuator on my line as a result.

The tech said he could observe interference coming from my SB8200 when it was hooked up to the cable line. The temporary resolution was for him to remove the attenuator, and replace the SB8200 with a Comcast SB6 at a cost of $13/month. He said my modem was defective.

Since the modem was under warranty, I made a claim with Arris and printed a shipping label to send it back. My new SB8200 should arrive within a week.

Does the above make sense to anybody ? I had quite a lot of trouble 2 years ago with Comcast to get a working signal. That included many modem changes, from an MB8600 to an SB6 to finally an SB8200. It took Comcast 6 months to get my signal working without dropouts. I am at the very end of a cable line on a hill. I have nothing else hooked up to my Comcast cable, just the modem.

So,  did my particular SB8200 unit really go bad ? Or is it a case that Comcast just doesn't want to support the SB8200. I want to know if the Comcast network team is going to start hounding me again when I hook up the replacement SB8200 in a week.