Thanks! Updating to the official HA image and docker-compose seems to have worked (like you mentioned, it was probably the "priviledged: true" missing that was causing the issue.
I've just worked out how to add the sensor, and it seems to be working! Although the button is not working very well. I popped the cover off and it seems the button is not attached properly to the circuit board, I managed to use a screwdriver to get it into pairing mode but I'm gonna try to get a replacement one.