I have a galaxy s7 edge. Zwift Android beta reads the wattage from my wahoo kickr fine, but fails to control the resistance whether in sim mode or erg mode.
Galaxy S7 w/ Kickr Core here, it’s worked for me a couple of times including controlling the resistance.
One time it wouldn’t work so I quite the app and went back in and it worked again.
I have problem too, with S7 on Tacx smart trainer.
Trainer have lost connection always to ZWIFT, it cost me a while to figure this out.
For indoor cycling Zwift plus Tacx smart trainer i use always my old Samsung S4.