FYI, I have had about a 20% dropped packet rate for the past day. Had multiple calls with Xfinity and no fix. I noticed I had T4 errors and that my upstream channels were listed as "partial". My upstream light on the modem was blinking instead of a solid color. I did a factory reset on my modem ( I own my modem which is a Netgear CM500). After the factory reset, it pulled the new signal settings and I am now 100% back in business.
I'm assuming something was changed in my signal from Xfinity and the modem was "hard set" to previous values so the factory reset cleared the old values and allowed the new settings to be applied. Just a theory but it worked.