Specialized TCU heart rate (Apple Watch) to Karoo

I have a Specialized Turbo Levo Gen 3 with the MasterMind TCU. I recently tried out the new Specialized Apple Watch app and really liked that it can transmit heart rate data from the Apple Watch to the TCU. I can see the heart rate data on the TCU display and also in the Specialized iPhone app – it even gets logged properly.

However, I'd really like to see this heart rate data on my Hammerhead Karoo as well. The Karoo detects the TCU as a heart rate sensor and pairs with it successfully, but it always shows 0 bpm, no actual data is coming through.

The issue isn’t between the Apple Watch and the Karoo, but rather between the TCU and the Karoo. It doesn’t matter whether the TCU gets heart rate data from an Apple Watch or a Polar HR strap, in both cases, it ends up sending a heart rate of 0 to the Karoo.

Has anyone tried this setup? Has anyone had success getting the Apple Watch heart rate (via the TCU) to show up correctly on the Karoo?