mike, what are you going to do? Flash the kernel? Then you are missing the --flash-only=kernel flag (most probably from above try). Or try to flash the named image (then -F instaed of -a, but that will flash your rootfs)? And no, this has nothing to do about "unlock". With above flashed kernel you will enter "open mode" with all other optimizations/pros/cons/problems. Read about open mode and password/accounts problems and make yourself a clear view if you are ready for that. You may also have a look at ubiboot thread of juiceme!