Check your userlibs. In your Mendix directory you have userlib directory. Double check if you have double jar files there. See also for instance the latest release notes:
Library Upgrades: (Ticket #172523, #173264, #175781)
- org.bouncycastle: bcpkix-jdk15on-1.69 to jdk15to18-1.70
- org.bouncycastle: bcrov-jdk15on-1.69 to jdk15to18-1.70
- org.bouncycastle: bcutil-jdk15on-1.69 to jdk15to18-1.70
After upgrading to the latest version, there could be a potential issue due to conflicting Java libraries of the old and the new version.
Hence it is recommended that you delete all Java libraries used by the old SAML module from the userlib folder of the project before upgrading to the latest version.
But it could also be other modules that might cause double userlib files.