Speed issues but only in races


I am trying to work out an issue when using my Kickr Core and Zwift.

When riding normally, my speed is very responsive and changes quickly, in-line with effort and terrain.

When riding in a race (with both normal and TT bikes), I am spinning around ~80RPM, 250W, 3.2FTP off the start line and find I accelerate quite slowly. The speed then seems to plateau around 40KPH and varies slightly depending on incline/decent but not much. If I push super hard to 500-600W and well over 100RPM on a 0% incline, the speed doesn’t increase. If I spin at 100W, it stays the same. Of course, in races EPG mode is disabled. It’s like my profile has a rubber band effect being applied during races (only).

This is ruining races as I’m quickly overtaken and it doesn’t matter how much effort I put in, the speed just doesn’t adjust accurately.

I have run multiple spin-down tests in both the Wahoo app and in Zwift.

I have checked firmware/apps/systems are all fully up to date. I’ve reset everything and the same in all different ways I’ve tried using Zwift.

The experience is the same consistently and it doesn’t seem to matter which method (see below) I use. ‘Free riding’ = all fine. ‘Racing’ = speed weirdness.

I don’t have another speed sensor I can use as of course the cassette is directly attached to the Kickr.

My WiFi is very stable. I have full signal strength and have a 500MB FTTP connection (speed test/latency etc on mobile devices and the Apple TV all show full speeds).

I’ve tried the following combinations:

Apple TV 4 + Pixel 5 (Android 12) - supports both Bluetooth and ANT+ + Companion App
Apple TV 4 + iPhone 7 (latest iOS) + Companion App
Apple TV 4 - Direct Bluetooth connection
Android - Direct Bluetooth connection and ANT+ connection
iOS - Direct Bluetooth connection
Windows 11 (Dell XPS 2020 13") - Direct Bluetooth connection
Windows 11 + Android + Companion app

Any ideas?