For only one project, i don't know why but Jira Admin gets assigned when i switched to the issue state 'Release Note' (when Release Notes have to be updated).
My workflow says that at the transition to this state, the issue should be assigned to the 'Release Notes Writer' role. At first, the project had no user for that role, so i assumed Jira Admin had been selected by default. But even after setting the filed, Jira Admin keeeps getting assigned to that state for new issues.
The user's group has the assignble permission in the permission schemes, and the issue is aparently there for any user that is in the Release Notes Writer role. the project has no Default assignee
The isue is not there for any other project with the same workflow and permission schemes