we have a strange problem with autovacuum. We have three workers, but usually only one works and two are waiting as they are all trying to process table pg_shdepend which is shared between all databases.
I hit the same issue when we've migrated out all large objects (~200Gb total), I've executed `vacuumlo` and then all autovacuums started to process `pg_shdepend`.
They've been picking on this table over and over again from different databases, but were stopping on the truncation phase due to other autovacuums were waiting on the same table.
I ended up manually vacuuming this table in the database, that was cleaned up, and also in the `postgres` DB. It fixed the case for me.