Issue with face shadow texture looking jagged

Hi, I’m working on a toon shader in Unreal. I set up a face shadow texture for the facial shadows (please refer to the attached image for my node setup). However, contrary to the preview, the resulting shadows are extremely jagged. I’d appreciate any advice on how to resolve this. Thanks!

As a new user, I’m limited to uploading one image per post. I have attached the rest of the photos in the comments below