Back button focus (bbf)

[DBphoto]

I have a Sony a77ii which I have set to bbf, setting AF w/ shutter to Off, and putting the AF/MF Button to emulate AF On. 
My software version is 2.00

This setup works fantastically well when working, but intermittently the camera sets back the AF w/ shutter to On (often at startup).
Then I set it back to Off and after a while it is back on On again. And so it continues.

Is there a way to set this function so that it stays Off?