Posted about this yesterday. Zwift on the iPhone 8 is not showing the correct cadence. I’m using the Wahoo RPM sensors. The correct cadence is showing on my head unit but according to Zwift I’m only doing 20-50 rpm when in reality I’m doing around 100 rpm. I’ve narrowed this down to a problem with the iPhone 8 itself because I ran Zwift on my old iPhone SE and the cadence is fine. Does anyone have any idea how to solve the issue or is the phone faulty? I’ve had no issues with any other Bluetooth devices.
Bluetooth only allows one connection to any device or app at a time so I don’t know how you are connecting a Wahoo S/C to both Zwift on iOS and your head unit.
I’ve got a similar problem using a Tacx vortex where I’m pedalling at around 80 rpm but the screen is fluctuating anything up to 150 rpm, which then appears to play havoc with the power output and speed on Zwift.
Vortex is connected to lap via Ant+ with an extension lead, no other magnets or sensors are working on the bike