A new firmware update with build number 23.1.A.0.726 has started to roll for the Sony Xperia Z2. This is the same update that recently hit the Xperia Z3 series. The update is live across a number of regions including USA, Hong Kong, France, Germany, Portugal and Spain. It is said to bring a number of bug fixes relating to notifications on the lock screen as well as providing a fix to Vivid mode and X-Reality.
Thanks Tamás and Antonis!