Booloader,boot and dtb.img is from stock/manufacturer firmware?
System partition is not burn correct on flash try burn again.
Maybe original boot.img(kernel) not mount system partition without some encryption security.
You need to stop u-boot with any key on keyboard (enter) and type "fastboot" in u-boot
example g12a_u212_v1#fastboot and you can use fastboot to flash firmware.
This is vortex firmware aosp v2.3.0 version but with beacon bi60r bootloader,boot,and dtb.img.