I just wanted to say that I've been experiencing the same issue, I'm not sure if it's packet loss or just high latency spikes but I notice it while playing a game (in my case the game is Old School Runescape). I've tried switching ISP but that didn't really fix the problem, I get latency problems using both ethernet (via powerline adapter) and WiFi. I think the next thing to try would be to switch to a different router/modem (I'm currently using the ISP provided one). If you ever figure out your problem let me know what your solution was.

Others that play the same game don't seem to experience the lag spikes as badly as I do, but I'm not sure whether they just get routed differently or if the problem is in my house or close to my house :(