Here are the steps to reproduce the issue from scratch:

1. Install a fresh JIRA instance and install the Greenhopper plugin.
2. Create two new Epic tickets (TESTFIRST-1 with Epic label 01 and TESTFIRST-2 with Epic label 02) with the "create issue" (link or button) on the JIRA dashboard.
3. Lock JIRA and reindex.
4. Try to create new issue with the "create issue" (link or button) on the JIRA dashboard, and open the Epic link drop down menu. It appeared that the Epic label is mismatch with the Epic ticket
   

PS: the issue is not reproduced if the first Epic is created via the scrum board of JIRA.

Workaround:

1. If you start typing a string, the suggested list will be corrected
2. Use GreenHopper's planning board to assign Epics