[Koha] OAI-PMH Set Question

Hi, everyone, I'm a bit of a Koha newbie so I hope this is the appropriate place to send this question. I am trying to set up an OAI-PMH set in Koha that looks in the 949 field, $a for OUWKanopy. This info is definitely in the MARC records I've uploaded but for whatever reason, I get an error from Koha saying the set is empty. To make things stranger: Koha accepts a set I created where I have it looking in a custom 909 field $a field I set up, again looking for OUWKanopy. When I run this set, it seems to pull data fine. Am I missing something here as to why data can be pulled from one set and not the other? Thanks in advance for your help,