Sony has just launched a new firmware update for this phone model brings 14.1.B.1.526 code, look at the numbers, you can see this is a slight upgrade from the current Firmware 14.1.B.1.510. No specific information on the change, but it is better that you just update via PC Companion tool.
.jpg "Xperia Z Ultra started a new firmware update (14.1.B.1.526)")
Source: XperiaBlog