SQL> purge dba_recyclebin; purge dba_recyclebin * ERROR at line 1: ORA-00600: internal error code, arguments: [ktcdso-1], , , , , , , , , , , 
It doesn't matter if the recyclebin is on or off.
I have done about six upgrades and this is the only db with the problem. I can backup this db using RMAN and restore it on another host and the error still gets generated.
I have about 43 objects owned by SYS and named WRH$* left in the recyclebin after the upgrade, but these are normal after the upgrade. Or, at least, I have these objects in the recyclebin after every 10.2.0.5 -> 18.104.22.168 upgrade I've done so far.
I can purge the objects individually to get rid of the immediate problem, but I am most concerned that this will show up again in another db.
I couldn't find anything on metalink. I've had a TAR open with Oracle Support for well over a month and it's going nowhere.