I would do a defrag Enough. It sounds as if your computer is trying to process the data sent at the end of the round and is taking a bit longer than it normally would, thus causing your computer to spike up. Though why this would affect latency I don’t know, does it freeze up for a moment at the end of the round or is your ping just spiking up to ~200 at the end of every round? Could just be that it is processing a lot more data sent from the server and that you aren’t getting it fast enough and then spiking up when downloading the end of round data.
What are your rates? I’m going to assume 100/100 25000 or 75/75 20000 if you let the server dictate them for you. If they’re 100/100 25000 I suggest lowering them all the way to see if that solves the problem and then raising them ever so slightly every single round if it indeed fixed the problem.