Hi @Michael_Bennett4! Welcome to the forums! I’m Francisco from Zwift Support.
Having your avatar suddenly slow down mid-ride sounds like such a bummer—it’s the last thing you want when you’re trying to enjoy the route.
Something else to add. I looked at your log server files and noticed that you’ve recently run Zwift in-game version 1.85.0. Can you try to update to the latest version of the game 1.86.0 to see how it behaves?
So far, your AppleTVOS seems to be updated: 18.3.1 based on Apple releases. However, try the steps that Steve mentioned previously. Try another route to see if the behavior occurs only in specific routes. Keep us posted.