I recently ran into an odd situation where I add a couple new user groups, the 21st and 22nd group, and wanted to add those groups to a project permission scheme. The group names were not visible in the drop down list box (DDLB). At the top of the DDLB the text says "showing 20 of 22 matching groups". JIRA does not allow me to select nor reduce the list by entering text to find these newly entered groups.
I have to go out and delete a few groups to be able to select the groups that I want to set permissions with.