EOS R AF disable in back button focus

[deleteme]

The title is a bit misleading as what I am trying to do is stop the R from focusing when I am shooting brackets.
I currently have the * set for AF start. Works great.
But when I put the camera on a tripod and use my CamRanger to shoot a bracket of 5 or 7 images it will re-focus on each frame. The result is that each frame can be slightly misaligned. Annoying but easily fixable.
What IS a problem is that sometimes the exposure is so underexposed the camera cannot focus and will not make an exposure. I have switched from focus priority to release priority but haven't seen the issue crop up yet. I am hoping that fixes it. Failsafe is switching to MF. But the problem then is forgetting to switch it back to AF.
My mk4 has no such problem even though it is set to focus priority.

 

[Chris.Chapterten]

What lens are you using? And is this happening in very low light levels?

 

[Frodo]

Why don't you use the hdr mode in the camera? I find that +- 3 stops is plenty and haven't seen any focus shift.

 

[deleteme]

It happens with any AF lens. The camera will check focus then fire. It makes slightly misaligned images as the lens stops at a slightly different position because of native slop in the system to effect quick AF. That is problem one.
Problem two is that when light levels are low or the AF point is set to some area that it cannot focus on, it will not fire.

 

[Dmcavoy]

It definitley sounds like something to do with the way the cam ranger is set up.

I shoot 5/7 bracketed shots on my R often, however I just use the countdown timer to release the shutter for the whole sequence and it doesn't try to focus between shots.

Have you tried without the camranger and using some other remote trigger to rule it out? Even with the EOS app?