Calibre changing metadata in content.opf?

Hi all! We use Calibre quite a bit for our eBook conversions, and we've noticed an issue in the content.opf file. ISBN's that we assign get swapped out when any editing is done in Calibre. Example HTML here-

<dc:identifier id="ISBN-978-1-4835774-1-8" opf:scheme="URI">ISBN-978-1-4835774-1-8</dc:identifier>
<dc:description>-</dc:description>
<dc:publisher>Kenneth Michael Jones</dc:publisher>
<dc:contributor>-</dc:contributor>
<dc:coverage>-</dc:coverage>
<dc:date>2016-08-04T04:00:00+00:00</dc:date>
<dc:rights>-</dc:rights>
<dc:subject>-</dc:subject>
<dc:language>en</dc:language>
<dc:identifier opf:scheme="calibre">631315c5-f643-4d82-9545-cd89f11d6abd</dc:identifier>

The dc identifier in the first place is the ISBN (which is correct) but then when Calibre starts editing, the second dc identifier line replaces the ISBN with that string of code. We currently have to go in on every book prior to saving and plug the ISBN into that line instead, or it fails delivery to a few different retailers (Apple is one of them).

Anyone else see this before and are there any existing fixes so we don't have to do that for every file?