Severe Packet Loss on Weekday Evenings

Early in July, a power surge/lightning strike killed my modem and router. Since then, after getting a new modem and router, I have experienced severe packet loss of around 30% on weekdays on a nightly basis primarily between the hours of 7-8 PM. I experience the issue on multiple devices, and I confirmed that it was present even when connected directly into the router, and even a second router still experienced the same issues. I used a ping tracker and could see that while the issue was occurring, the issue was beginning upstream of the router, at the very first hop, which leads me to think that a local node is the cause of the issue (and may have been damaged in the same storm that took out my first modem/router.) How do I have this issue investigated?