A77 flash overexposure problems: hypothesis

Has anyone got these intermittent flash overexposure problems while using fixed low ISO? Or fixed high ISO and distant subjects? If my hypothesis is correct, they won't.

Using fixed low ISO with my A77, and using both pop up and HVL F43 flash on and off camera, I haven't seen these problems -- yet. So that could just be good luck so far, and perhaps there are some A77s without this problem, and luckily I've got one.

--
Chris Malcolm