I can second this complaint. Every so often the Internet performance drops considerably. Observed symptoms include lengthy video buffering and (separately) Cox blocking / throttling many web sites but not all of them. When my browser reported "Site xxx is not available / took too long to respond" I opened a CMD window and was able to ping each and every one of them. Timing was very reasonable, 10ms to 15ms each, proving my Wifi, my router and the website itself were OK. Still, Cox did not pass through the other internet protocols (http, https, etc.), thus blocking them. A call to the Cox tech support was useless. I was told to [a] call the modem/router tech support, or [b] pay Cox $10/month for access to their expert tech support. The tech support agent told me they see Internet working so from their perspective the problem must be on my end.
Neither answer addressing the underlying clear issue. The internet connection came back to a reasonable behavior after a couple of hours - no obvious reason why it happened initially or what brought it back.
We should receive quality and reliable internet connection for the fees Cox collects.