AOSP Android 11.0 for XZ1C - boot.img fail to flash

[user2647]

Hello.

I've managed to build AOSP Android 11.0 for XZ1C following the guide:
https://developer.sony.com/develop/open-devices/guides/aosp-build-instructions/build-aosp-android-android-11-0-0
But on step 8 I'm unable to flash "boot.img" output file - when executing command:
"fastboot flash boot .../boot.img​"
I get error:
"fastboot: error: cannot get boot partition size"

Other image files (recovery, system, userdata, vendor) are flashing Ok.

I've tried to flash boot.img with command:
"fastboot flash:raw boot .../boot.img​"
Here I do not get error message, but after that the device does not boot to the system - it reboots itself 3 times and then hangs with black screen.