oem rman backup rewrite oratab

I have oracle cloud control 13c.  I have an older 12.1.0.2 dB that is in nonarchivelog mode.  When we do a cold backup each week we shut it down via the job via OEM and perform the backup and then run alter database open.  Somewhere in the middle of that the agent sees the DB is down and removes the entry from oratab and then puts it back in after it is back up.  At least that seems to be what is happening.  The issue is it seems to get the oracle home that is in correct.  It adds a slash after the actual oracle home.  Where does the agent get the oracle home from or am I getting this all wrong?