Last days, I had an interesting issue with a customer’s test database. The DB crashed, after manually but unintentionally corrupting the SYS schema (dropping an unknown number of objects). Restarting the instance (open) ended with:
ORA-00600: internal error code,
arguments: [kokiasg1], , , , , , , , , , , 
Our quick fix was to restore/recover (PITR) to a point in time before causing havoc on the SYS schema. But as a spin-off, the Oracle Support SR I did start in parallel, analyzed the cause of the ORA-600 [kokiasg1]. I did not find anything reliable on the web, but this is what my support engineer suggested, if a PITR like in my case would not be possible due to business data requirements:
ORA-600 [kokiasg1] error can also occur if the sequence IDGEN1$ is missing, not only AUDSES$. The sequence IDGEN1$ is created when the database is created. The ddl is also in script migrate.bsq.