Getting some concerning errors in one of our databases that is on 9.5.11, on autovacuum from template0 database pg_authid and pg_auth_members. I only saw some notes on the list about this error related to materialized views. FWIW, we did use pg_upgrade to upgrade this database from 9.4 to 9.5. Here is an example:
2018-03-19 12:08:33.946 CDT,,,14892,,5aafee91.3a2c,1,,2018-03-19 12:08:33 CDT,59/340951,0,ERROR,XX001,"found xmin 2906288382 from before relfrozenxid 740087784",,,,,"automatic vacuum of table ""template0.pg_catalog.pg_authid""",,,,""
2018-03-19 12:08:33.957 CDT,,,14892,,5aafee91.3a2c,2,,2018-03-19 12:08:33 CDT,59/340953,0,ERROR,XX001,"found xmin 2906288383 from before relfrozenxid 740087784",,,,,"automatic vacuum of table ""template0.pg_catalog.pg_auth_members""",,,,""
Any insight would be much appreciated.