After upgrading from 13.0.0 to 13.5.0 the server starts logging these errors into CoreSystem debug log:
This happens because the DevicePrintModule has been removed from 13.5 but the upgrade process is not correctly removing it from the authentication configuration.
- Install OpenAM 11.0.3 and create a new DevicePrintModule authentication module instance
- Upgrade to 13.5.0
- access http://openam.example.com:13080/openam/XUI/#realms/%2F/authentication-modules
Removing org.forgerock.openam.authentication.modules.deviceprint.DevicePrintModule manually from the configuration with ssoadm unregister-auth-module stops the errors.