This is caused due to bug NVBU-19634 when NetVault Server attempts to access an oPluginOptionsScreen object that is NULL.
Steps to reproduce the issue:
1. Install NetVault Server v12.4 (e.g. 12.4.0.13)
2. Have an Oracle Client; NetVault version can be any on the Oracle client. What is important to reproduce the issue is that the version of NetVault Server has to be v12.4
3. Configure Oracle Client to perform CLI backup or restore to the NetVault Server 12.4
4. In the Oracle Client, perform a backup or restore job from Oracle RMAN CLI
Observed Result: In NetVault WebUI, Job Manager dies; in Oracle RMAN CLI the job hangs, and needs to be aborted in RMAN (CTRL+C)