Manufacturing defect?

[Frank Bombardiere]

What would cause these strips of missing granules. Notice that the missing granules are all underneath the architectural layer of the shingles.

[Frank Bombardiere]

The photos did not upload the first time. Here they are.

[Scott Patterson]

It looks like a manufacturing defect.

[Frank Bombardiere]

Thanks Scott, I should have asked the question differently. I was wondering if anyone had an idea of what in the manufacturing process would cause this.