So now that we have it narrowed down to the possible location of the issue (between the computer and hop #1), and the time frame of the issue, it is just a process of elimination from here.

The best way to troubleshoot is to evaluate and eliminate all variables. So starting from your computer, look at the cables and any joints or junctions before the cable goes into your modem. The best way to eliminate this as a possible variable for the issue is to get a cable (newer preferable) and plug that cord straight from the computer directly into your modem. No patches or extenders or anything. If, after you do this, the packet loss still occurs - then you can rule out the issue being your cable going into the attic and wrapping around the electrical line.

If this direct cable does improve your packet loss, then you can try running a new cable into the attic that doesn't wrap around anything - and go from there.

One last thing to consider - because you know a time-frame when it is happening, see if you can find a pattern of things that are going on at that time. For instance, if you have a roommate that gets on the computer at that time. Or if your computer or Xbox or something is set to install updates or do backups at that time. Things like that - which may be causing latency.

Go ahead and try this and let me know what happens.

Cheers!

-Phillip