There were issue fixed in latest 4.2.1, you can replace latest war file from here:
https://ox.gluu.org/maven/org/gluu/oxauth-server/4.2.1-SNAPSHOT/oxauth-server-4.2.1-SNAPSHOT.war
1. service oxauth stop
2. replace oxauth.war
3. service oxauth start
Also please check opendj log and schema file. As it was reported lately there were some corrupted packages with outdated schema, replace your local schema with this file
https://github.com/GluuFederation/community-edition-setup/blob/version_4.2.1/static/opendj/101-ox.ldif
(Opendj service restart is required).
Thanks,
Yuriy Z