Upload speeds are approximately half of the provisioned speed

I recently moved and brought my comcast XB8 modem with me. It is hooked up in the same configuration: bridge mode -> my eero system.

I have the same "Gigabit Extra" plan and my downloads are fine ~940Mbps. My uploads at the new house are 15-20Mbps. At my old house I would consistently pull 40-42Mbps upload. I have chatted with comcast reps online and they will "update the boot files" then reboot my modem and then my uploads are great, ~40Mbps. Then after a few hours everything returns to the 15-20Mbps range. I am stumped.

FYI, I am testing using the speedtest built into the ethernet hardwired eero and also the SpeedTest app on my windows PC that is hardwired.

Here is some info from the comcast modem page. Not sure if it is helpful. Thanks for your help!