Sony Mobile is rolling a new firmware update for the Xperia M4 Aqua Dual, which moves the build number to 26.1.B.2.102. The update is currently live for the E2312 variant in Vietnam and the E2363 variant in India. The E2333 variant has not updated to the latest build at the time of writing. The update is expected to bring a number of big fixes including better control of the heat issues some were facing.
Sony Xperia M4 Aqua Dual FTF firmware files – Android 5.0 Lollipop (26.1.B.2.102)