I have fully unlocked the Samsung device and I have downloaded the Kernel sources from the Samsung open-source site. I have built the kernel fine with instructions are given in the README_Kernel.txt file included in the source code.
I get the build output at out/arch/arm64/boot/Image.
I have also downloaded the firmware of the device from samfrew: G977PVPU2ASH6
I have extracted the boot.img of the downloaded firmware and patched the Image using AIK-Linux-v3.6
When I have flashed(with Odin v3.14) it then it's failed and stuck on Splash Screen(with information about phone status showing on it which I generally see in the download mode.) as following: 
This is the first time, I have built a kernel fine and get output. I have fixed the device by flashing the original boot.img from the downloaded firmware.
I want to understand why the kernel built from the source code failed to flash. I know a few reasons like:
- The possibility of Samsung doesn't share the full code because of proprietary reasons.
- Wrong toolchain.
How exactly, someone can determine the problem?Any help/suggestion?