I am not 100% sure what caused it as we simply deployed a new instance instance of upgrade. May be those who upgraded can share their views.
In any case, there is a reference to 'java' in your error log, and looks like starting with Unified Manager 9.5, OpenJDK is provided in the Unified Manager installation package and installed automatically. Oracle Java is not supported starting with Unified Manager 9.5. If it was a 'new install', it wouldn't have mattered, however b'cos it is upgrade, so I am guessing so.
Plausible cause: Directory /home/jboss was not created.
Thanks, @Ontapforrum I found the issue, We were upgrading multiple OCUM instances. All of them was 7.3P1, unfortunately, one of them was 7.1P3 which is not supported to directly upgrade to 9.5 hence this error occurred. I have updated to 7.3p1 then upgraded to 9.5P1.