I'm trying to understand why so many MOPAR trim tags / fender tags have erroneous mis-stamped numbers in odd locations. It almost looks like they went through the press with stuff under the tag.

They quite often have numbers or letters in strange locations (not part of the build information)....crooked....etc..

Is this just poor quality or were they done so fast that they often had stuff from the last tag under the one currently being stamped ?

Usually crooked or misaligned staps are actually inspectors' stamps - most common on Lynch Rd. cars. They appear as numbers/letters or punch marks.