I'm in the same boat now. They sent me the email about upgrading to DOCSIS 3.1 and checking into their other plans. I did that, and checked out Gigablast which is actually $3 a month cheaper than the plan I was on. It was blistering fast for a couple days and now for the last 5 days, just constant drops. Getting 800-850 down and like 0-5 upstream, maybe... I show 40-60% packet loss.
I ran diagnostics on my equipment, they are perfect, right in the sweetspot with Power, SNR on the up and down channels. Plus I know it worked great for a couple days, was getting like 850/35 constantly.
They have been telling me there is "noise" on the line and techs are working on it, but then I check their website and they say everything is fixed. Now it's starting to effect my job since I'm working from home.
Pretty ridiculous!