I have this randomly occurring issue (so far twice), that I want to see if I can maybe get a better response here. I called Cox for the same issue, but they insisted that there is no problem.
On the ONT, there are three lights, if you are facing the ONT, the one at the left most is the "activity light" that one that appears to blink rather periodically when working properly. So here is the situation, normally the activity light will blink periodically (at least that's what it appears to the eyes), I get a ping about 1-4 ms MAX, and upload speed is good. However, I have observed, twice now, there are times when the "activity light" will blink periodically like "blink blink blink blink" then will completely go away for roughly a second, then resume "blink blink blink...", and repeat. when this is happening, my ping will shot up to about 30-80 ms, although the upload/download speed seems to be about the same.
I have called Cox on this the first time, although I was told there is no problem that they can observe, and it's all normal. I can tell you that is not, because I'm looking at a ping that is 20-30 times longer. I can also tell you that there is no problem with my system, because the solution, is to wait it out, usually the next day everything goes back to normal, the activity light as well as the ping. Also the second time this happened was right after, we had a lost of internet (my surveillance camera sends a notification every 15 minutes when it lost connection to the internet). According to the notification there was a period of an hour which we do not have internet connection, and right after the internet is resume, the activity light and ping issue appears. Personally, I'm OKAY with this, because the service is not interrupted, however for Cox to tell me it's all nominal seems to be a bit weird.
I can't say that I'm terribly bothered by this, getting too old to get all worked up about little tech issues. But just figured that I'd share and see if anybody else is experiencing the same problem.