When I try to flash via fastboot system.img (from my custom AOSP build) to Sony Xperia Z3 I get the following error:
# fastboot flash system system.img
sending 'system' (584106 KB)...
OKAY [ 18.294s]
FAILED (remote: size too large)
finished. total time: 18.297s
I have finally found the solution:
in BoardConfig.mk was larger than it should be. Changing it fixed the issue.