Apple iCloud private relay

Noticed my internet download speed suddenly was < 10% of my subscribed speed.  I determined that performance returns to normal if I disable iCloud Private Relay on my apple devices.  I am using my own cable modem and router (no recent changes to this equipment).  Recently, Xfinity upgraded our neighborhood to the 10g network and my Mac was upgraded to the Sonoma OS.  Anyone know if this issue is an Xfinity or Apple issue?