ORA-00600: internal error code, arguments: [ktbdchk1: bad dscn], , , , , , , , , , , 
This is a database on 18.104.22.168 version, which is very important here. On first sight I have found that exists on the Metalink a bug (Bug 8895202: ORA-1555 / ORA-600 [ktbdchk1: bad dscn] ORA-600  in Physical Standby after switchover (Doc ID 1608167.1)), which happens after switchover, but version 22.214.171.124 covers also a patch for this one. And there are no other descriptions for that version, so there are only some suggestions, what to do to make the possible bug finding easier.
However when I read everything I have found that the fix is disabled by default. So I enabled it according to the article above and even though I was not sure if this is it (the trace messages were different than the ones provided in Metalink), it helped.
Please keep in mind the fix may blow up some queries, so one have to enable also another parameter (Bug 13513004 - ORA-600 [ktbgcl1_KTUCLOMINSCN_1] on blocks fixed up by 8895202 (Doc ID 13513004.8)).