glTF 2.0 Validation error: ACCESSOR_VECTOR3_NON_UNIT

Hello,

I’m getting an error from a .glb file that was exported from Blender using the glTF Validator. I’ve been searching online for the past couple of days, but can’t find any information describing what this error is all about and how I might resolve it. I’m fairly new to 3D modeling so any help to point me in the right direction would be greatly appreciated. Here is a snippet from the validation report:

{
  "code": "ACCESSOR_VECTOR3_NON_UNIT",
  "message": "Vector3 at accessor indices 4830..4832 is not of unit length: 0.",
  "severity": 0,
  "pointer": "/meshes/0/primitives/4/attributes/NORMAL"
}

What I need to know is, what is the error referring to, and how can I find the source of the problem inside Blender so that I can correct it?