Focus shifts

[Dvid Maguire]

I am currently using my Sony A7siii with a Sony GM 24mm 1.4 lens.

I have just recently been conducting interviews in the Australian outback (exteriors). Each interview backlit. I found regularly that the focus set in eye recognition drifts substantially during filming.

In the past year I have constantly , confidently relied on auto focus and eye recognition. Why all of a sudden is the camera doing this?

I have also updated the software recently.