Is my FIOS router the root of my problems?

I have already posted some of my issues to r/techsupport but I think this is a Verizon issue at this point. We are rather hardcore techies, but networking isn't my strong suit.

For the past two weeks, we've been having internet issues with both of our PCs, both are wired, running the most current version of windows (me 11, her 10), all LAN drivers are up to date, and nothing out of the ordinary has changed in the past few weeks that I can think of to change anything.

Getting on the internet is fairly fine, but on my partner's PC, google drive (chrome) keeps going offline, she can't upload images to Discord, and we are both having trouble loading some web pages. Most of the issues are occurring on her PC specifically, which is weird to me that it would only be on her PC.

I even tried to reinstall windows on her PC to see if that would solve the issues, but it hasn't. I also thought it would be our Norton causing the network issues but even uninstalling Norton on her PC and setting Windows Security up regularly it's still persisting. I clean booted into her Windows and it was still occurring.

I had gotten on the phone with a Verizon rep and they had used the troubleshooter a couple of times, but it still didn't fix the issue. They had me connect her PC directly to the WAN port on the ONT and all of the issues disappeared immediately. They thought it was the router, so I just go the new one today and I'm still having the exact same issues.

We don't have any crazy settings or anything on the Router, nor do we have Home Network Protection on, since I've seen that to be an issue others are encountering.

I'm lost as to what to do

I can only expect it to be a Verizon/network issue, nothing else makes sense to me.