Hi Wertandrew!
In your UEFN material, you are using the camera position as the input for your dot product while in your UE5 material, you are using the camera vector as the input for your dot product.
Since the camera position isn’t a normalized vector, the dot product result won’t be normalized and can lead to a very intense emissive color.
Try switching the camera position for the camera vector and hopefully you’ll get what you are looking for.
Cheers