Potential focus issues with AI Servo.......any suggesitons?

[MyEventPix]

Hi Cannonites, I'm having a couple of issues with my auto focus when shooting sports. Heres the stats
5d Mk4
70-200 f2.8 IS
F4.5 (for depth of field)
ISO 6400 or higher
1/1000th second
AI Servo single point
Back button focus
High speed drive mode
The majority of the images are fine but every now and then I get a few different issues.
Sometimes the focus point locks on and registers (using light room plugin to confirm in post) but yet the subject is not in focus, in fact nothing in the image is in focus, yet the camera registers a focus point has been achieved.
Other times the subjects face is wildly out of focus and their legs are in focus, when they're in the same focal plane.
Any tips on trying to resolve or am I always going to have to consign a % of images as waste?
Thanks

 

[Act444]

What case mode are you using? FWIW, I found the 5D4's AF tracking and accel/decel tracking to be a bit on the sensitive side at the default "0" setting - when I set both to "-1", my hit rate did increase slightly. Especially with a scenario like this where the subject would be moving at a constant speed without too much variability.