Like you, I spend a reasonable amount of time (in season) at both Conowingo and Bombay Hook and am surprised we never met. Perhaps, we'll be fortunate to connect up this fall? So, what I am particularly frustrated with is what I think you describe as "AF drift". Initial capture is achieved and then when the eagle strikes, the AF seems to drift off target for a few frames, only to reacquire again after the strike. These are head scratching sequences where one is panning a strike usually less than 50 yards away and the target is large in the frame (nearly occupying 80+% of the vertical field. How or why this occurs with my Z8 is simply perplexing as again, I've not experienced this with Sony/Canon. If they acquire AF, they don't seem to lose in through the strike. With respect to the reflection "latching", I've encountered this on rare occasion with the Z8 though if one "pumps" the AF, i.e. releases and reacquires, this usually resolves.
The thought of shooting a flat picture control is intriguing though it is difficult to see why that would affect AF? Conceivably, I could see how using the custom picture control which produces blinkies could tax the EXPEED 7 chip, though why would NL (what I use) rather than "flat" lead to drift?