5D IV Focus Issues

I'm somewhat new to the 5DIV, and I'm having focus issues - problems I don't have with my 1DIV.
I'm not using the custom/programmable/whatever feature; frankly, the instructions just confuse the hell out of me.  I'm thinking I'm going to have to figure that out eventually, but here's my issue now:
I focus near the (usually 100-400 II) mfd on a butterfly or dragonfly or something small.
A breeze blows the subject.
The focus then locks on the bg, and will not reacquire the intended subject unless I manually focus on it first.  (I’m trying to reacquire using bbf.)
I'm currently set for Case 1, tracking sensitivity at 0, accel/decel tracking at 0, and AF auto switching at 0.  
Honestly, I find all of this confusing as hell.
Ideally I'd like it to work for  BIF as well as the pseudo / quasi macro-ish stuff I shoot.
Suggestions?
Thanks in advance.

You might decrease your tracking sensitivity to -1 or -2.  Another thing to look at is your AF points.  For BIF I use center point expansion or single AF. Arash published a book on this a few years ago which I found to be very helpful.  http://www.arihazeghiphotography.com/Guides/

Craig Lipski wrote:The focus then locks on the bg, and will not reacquire the intended subject unless I manually focus on it first.  (I’m trying to reacquire using bbf.)

Make sure you have Lens drive when AF impossible set to "ON"

I've seen exactly the same symptoms described caused by that setting being off.

It's at the top of the AF menu 4 

Regards

Kev.

KeBul wrote:

Craig Lipski wrote:The focus then locks on the bg, and will not reacquire the intended subject unless I manually focus on it first.  (I’m trying to reacquire using bbf.)

Make sure you have Lens drive when AF impossible set to "ON"

I've seen exactly the same symptoms described caused by that setting being off.

It's at the top of the AF menu 4 

Regards

Kev.

Been there, done that. . . .