p.1 #5 · Best Aftermarket Battery Grip for the Nikon Z8?
I had a single incident with mine and then it cleared up and never happened again, so might as well take a moment to type it up.
I was at my sons soccer scrimmage and everything for the first hour, then I got an error saying the battery wasn't correct, possibly not original. My z8 then made a ka-dunk sound and turned off. Knowing my batteries were fine and worked previously I restarted my camera and the error occurred again in a minute and turned off.
I unscrewed the extender and put in a single battery. Worked fine. Swapped with the 2nd single battery. Worked fine. Put both back in the extender, made sure it was screwed in appropriately to bottom of camera, and it's never errored since. Just fyi. It likely was a mm loose and got confused on the connection(?).