Interesting setup — are you using in-body stabilization or relying on the lens’ OS when that jumping happens?
Also, have you tried turning off pre-release capture to see if it changes the behavior during continuous bursts?
Sounds like you might’ve had your autofocus mode or subject tracking set differently than usual — that Z8 can be tricky when you start experimenting. If everything’s fuzzy across the frame, it could be the camera grabbing focus on the wrong plane or using a slower shutter than needed. I’d go...