TACX Vortex resistance dropping out during a training session (eg climbing hills)?.

Anyone having an issue with the TACX Vortex resistance dropping out during a training session (eg climbing hills), that you have you been able to resolve?.
I use the TACX Vortex with Samsung A51 android phone hosting the Tacx training app. I am using my phone to connect via BT to the Vortex trainer plus a BT connected polar heat rate strap.
Approx halfway through a training session the Vortex resistance just falls off and its like I am cycling on the flat. Maybe the problem is that BT is only supposed to work effectively between 2 devices only, an addition device requiring BT may confuse the communication process, possibly??.

I will try again connecting only the TACX training app (on phone) to the Vortex trainer (without HT monitor) and see if it solves the problem.