I moved my main PC downstairs (which is where the router is located). The first thing I noticed when I moved it closer to the router was that all of a sudden the ping dropped back to the level I had previously. (That is to say, between 50ms and 150m…
I've never had to switch to cabled gaming before but I can try that sometime. So far doing a complete wipe hasn't eliminated the problem (even deleting the whole folders after uninstalling).