Connectivity issues nightly/high packet loss and jitter

For most of the day I'm getting fantastic speeds and no problems at all, but for the past three weeks between the hours of 8-10PM I'm having serious internet connectivity issues nearly every night. When I use the internet speedtest tool from Cloudflare I can see absurd (25%+) packet loss and signal jitter (sometimes as much as 900+ms). My wife has been picking up extra shifts and working from home recently and this network behavior immediately disconnects her from her work and VOIP. Restarting the Xfinity modem does nothing, and I've even spoken to a few neighbors who are also having the same issues and have had techs to their homes to no avail. At this point this is causing my wife a lot of undue stress and I'm really just looking for a solution before this becomes a larger problem for her.