Not sure if this should be an answer or a comment.
Your description feels a bit like https://bugs.gentoo.org/show_bug.cgi?id=359671. Although some parameters of the situation seem to be different, esp. the fact that you don't even have a cable connected to realtek, I guess it can still possibly have something to do with the realtek driver's wonkyness and it's probably worth it to throw this idea out here.
So try blacklisting the realtek modules.