Garmin 945 dropping HR and Cadence on runs?

Hello everyone, I’m new to Zwift and loving it so far but I’ve developed a problem, I’ve tried searching but can’t find a solution.
Today for the second time, I started a treadmill run and everything is great, my 945 is connected to my Samsung Galaxy 10 for cadence and speed and I have a chest HR strap supplying the HR data.
After 15 minutes the HR and Cadence drop out and my avatar continues to run at the pace I was going when it dropped out. Even if I adjust my pace or completely stop running my avatar continues to run at that pace. Exactly the same thing happened last week only at 20 minutes in??
I use my laptop and Garmin Edge when on the bike and don’t have any issues.
Any ideas.

Are you using the virtual run option to link to Zwift?