adpatch: Drop FND_INSTALL_PROCESSES table [No] ?

When using adpatch to apply a patch, it reports an issue and I had to make the choice: 

Creating the AD_UTIL_PARAMS table...
Table AD_UTIL_PARAMS already exists, so dropping the table and recreating it.
Creating FND_INSTALL_PROCESSES table...
The table FND_INSTALL_PROCESSES created by AD Administration already exists.
If you are sure you do not want to keep the information from the failed
AD Administration session,you may drop FND_INSTALL_PROCESSES table and
continue with AutoPatch.
If you choose not to drop FND_INSTALL_PROCESSES table, AutoPatch
cannot continue successfully.
Drop FND_INSTALL_PROCESSES table [No] ?

The problem is an error from a previous session of adadmin. But the error was ignored.

After I answered Yes in above adpatch session, the session completed with the real error. 

AutoPatch error:
The following ORACLE error:
ORA-04045: errors during recompilation/revalidation of SYSTEM.LOGIN_AUDIT
ORA-01031: insufficient privileges
ORA-01434: private synonym to be dropped does not exist

occurred while executing the SQL statement:
DROP SYNONYM AD_DEFERRED_JOBS
AutoPatch error:
Error dropping FND_INSTALL_PROCESSES table

You should check the file
$APPL_TOP/admin/<SID>/log/xxxxx.log
for errors.

I checked back adadmin log and saw adadmin had the same error which is caused by custom trigger SYSTEM.LOGIN_AUDIT in the database. If the problem is not fixed, AD utilities (adadmin, adpatch, etc) will keep getting the error. After I dropped the trigger from database, the problem does not show up again.

The lesson is I should check adadmin log carefully even for a simple run.