Did the H10 properly connect and record during the first workout (threshold block session), and only experience connection issues during the second (Extra Shot)?
I and a number of others have repeatedly experienced issues with SYSTM disconnecting heart rate monitors in between sessions (restarting a workout or finishing a workout and starting a new workout) and being unable to reconnect without multiple troubleshooting steps that only sometimes randomly work less than half the time. In my case, this occurs with SYSTM on the iPad with both H9 and H10, and has continued to happen both when they are new and when they a year or two old, and near full battery capacity.
I genuinely think the problem is just that the SYSTM code handling Bluetooth connections is pretty flaky and has not been appropriately updated, as I have never experienced this issue in any of the other five or six cycling apps I’ve used on my iPad (including RGT!).
For example: