Cadence issue with Trainerroad when running Zwift and Trainerroad concurrently

I am able to use Zwift and Trainerroad together using an iMac and Bluetooth. This works well except the cadence reported by Trainerroad jumps all over the place, usually downward. I have been back-and-forth a few times with a representative from TrainerRoad, but the problem is unsolved.

Here’s my setup:

Trainer: Zwift Hub.

Computer: iMac from 2017 with latest operating system.

Connections: Connect first to Trainerroad. Zwifthub is the trainer, using bluetooth. Then connect to Zwift. Power source is Favero Assioma pedals using bluetooth. Cadence is Favero Assioma pedals using bluetooth. (See my screen grab). I did a ride today, and Trainerroad reported an average cadence of 72, when it was actually 83. Trainerroad also missed my cadence peak of 187 when I sprinted in a low gear.

When I use either Trainerroad or Zwift by themselves, there are no issues. I have also tried using various combinations of ANT+ and Bluetooth, with no resolution.