Elemnt to control trainer, wrong power source

I’ve asked wahoo and they say it isn’t possible but I’ve used my roam to control my trainer and using my assiomas as power source. For months this can work without any issues but suddenly the roam (and I have had a roam 1 and 2 with the same issues) will use the trainer as power source instead of the trainer (I also have 2 trainers, a kickr v5 and an Elite Nero and it happens with both trainers). Usually I remove all the sensors, power off everything and re-add and this can fix things again for month but not always. Does anyone have a solution? (I really want to track my l/r balance because I had a huge imbalance)