Blue tooth connection to BMPCC4k

I have been controlling my BMPCC4k over blue tooth app on my phone and due to the distance and building construction the connection is very unstable causing me to have to run up and down a spiral stair case during a church service to refocus the camera. I cannot use control from my atem mini pro as I am using a fibre HDMI.
Is anyone aware of a good blue tooth range extender to link my phone to the camera stably or any other options that may work.
Thanks for your time Steve