Yesterday, I upgraded both my D500 and D850 to their respective firmware updates. Rebooting the D850 on v1.02 failed with no battery/flat battery symbol. Ahhhh! the camera no longer recognized the Hahnel ENEL18 battery in 3rd party Mcoplus grip. Yet it worked fine with the OEM ENEL15a.
Conversely, the upgraded D500 on v1.15 works fine with the same Hahnel battery in the Meike 3rd party grip that I've used without a glitch since late 2016.
So.... it either the v1.02 in the D850 eclipses functionality of the Mcoplus grip, or the Hahnel ENEL18 (?). Does this experience reveal more changes under the hood by Nikon - beyond the 1 minor fix stated in timezone settings?
UPDATE : following advice on dpr, I just re-installed v1.02, then removed the Hahnel battery and re-inserted it. So the D850 still does work fine on Hahnel ENEL18 in Mcoplus grip. Gives 9fps and I also appreciate the extra ++ battery life it allows for Liveview work