Error occurs on Compiling global shaders during cooking process

Hi, I am new to UE4 and using FaceARSample project and have been trying to make a build for iOS device.
I still continue experiencing same error on compiling global shader. (according to the error logs below)
I hope someone can help pointing me in the direction of understanding this issue and finding a solution.
Thank you kindly

LogShaders: Warning: Compiled 456 global shaders
LogShaderCompilers: Error: Errors compiling global shader TSlateElementPSFontfalsetrueA :

2020-01-29 19:51:02.122 UE4Editor[36259:124364] Fatal error: [File:/Users/build/Build/++UE4/Sync/Engine/Source/Runtime/Engine/Private/ShaderCompiler/ShaderCompiler.cpp] [Line: 4376]
Failed to compile global shader TSlateElementPSFontfalsetrueA . Enable ‘r.ShaderDevelopmentMode’ in ConsoleVariables.ini for retries.
LogShaderCompilers: Error: /tmp/2352_283414336.metal(0): Failed to load output file: /tmp/ShaderOut8449A4E25947BD2BE6248DBD8A4C6D41
LogMac: Error: appError called: Assertion failed: [File:/Users/build/Build/++UE4/Sync/Engine/Source/Runtime/Engine/Private/ShaderCompiler/ShaderCompiler.cpp] [Line: 4376]
Failed to compile global shader TSlateElementPSFontfalsetrueA . Enable ‘r.ShaderDevelopmentMode’ in ConsoleVariables.ini for retries.