Canon R6 Mark II focus issues

Hi
Just wondering if anyone else is experiencing inconsistent focusing with the Canon R6 Mark II.
I mainly shoot actors in the studio using strobes. I’m using my EF 24–70mm via the Canon adapter ring. I’ve turned off all automated subject/eye detection and am working purely with Spot AF for precision, selecting the closest eye manually — but I’m still finding focus to be hit and miss on some shots
Even in good light, static subjects, and controlled studio conditions I’d expect it to be rock solid, but I’m occasionally getting focus landing slightly off where I place the AF point. What’s more concerning is that sometimes the focus is completely off across the whole image, not just slightly!. In 17 years of shooting professionally I’ve never experienced this kind of behaviour. I’ve now tried two brand new R6 Mark II bodies and both are doing the same thing.
Also, when half-pressing the shutter to focus, the image in the EVF/LCD sometimes blows out almost completely white. I have exposure simulation (adapted lighting) turned off, so I’m not sure why this is happening.
For context, I never had any of these issues with my 5D Mark III in the same studio setup.
Could this potentially be the EF–RF adapter causing problems? Has anyone else seen similar behaviour with adapted lenses on the R6 II, or found any settings tweaks/firmware fixes that improved consistency?
Thanks in advance.

 

on a couple of my wildlife channels an rf body and ef lens combo has had focus issues and its been put down to the speed of communication between body and lens not giving the older ef motors time to acquire focus in conjunction with the read out speed of the sensor while continuous auto focus is being held down
i dont know if thats the same thing you are having, thier fix for this was to not use the continuous auto focus while the subject is still in the same focus plane, alot of those wild life smudgers use back button focusing which separates the auto focus and shutter actions so its a relatively easy adaptation.

there is a section in this video 'about that auto focus' on the time line which starts from 13:15 to 30:22 that may have some information value either directly or just in general