After upgrading the plugin to 4.9, users with credentials create/update permissions at the folder level, lost ability to add or update credentials of any type.
We had to role back the plugin to version 4.7 to resolve the issue . This issue has been acknowledged by CloudBees as well - we are on CloudBees Jenkins Enterprise 2.289.2.3.

We reported the issue https://github.com/Blazemeter/blazemeter-jenkins-plugin/issues/89 as well .