Share your experience!
There is no 5.1 for Z1 yet as far as I know. See this older thread,perhaps it helps:
/t5/Xperia-Z1-Z1s/screen-won-t-lock-during-a-call/m-p/801483#M32262
/t5/Xperia-Z3-Z3-Dual/Notification-bar-is-opened-with-just-a-tap/m-p/930884#M9371
/t5/Xperia-Z1-Compact/Info-bar-during-phone-calls/m-p/1030485#M17627
Is this the issue you encounter?
Strange, I didn't have that on Z1 or Z2. Are you sure the sensor is working properly?