Thanks for the tip, that’s a cool technique to know! Although the issue doesn’t seem to be caused by lerping two normals - video also does it earlier in the process. I did try it tho, and the issue is still there. Although it seems that the normal that is applied from the Input is completely broken as can be seen in the preview - it’s single color instead of actual supplied preview.
The normal that Texture Sample outputs is not same as preview I feed into Input Normal and I am not sure where it goes wrong.
EDIT: Nvm, after some… random attempts switching stuff the setup from video suddenly started working. Thanks a lot! 
