I run the above query (also without restricting to pg_catalog) under superuser postgres in both dbs.
There was no error.
The databases are on SSD, no problems with storage so far (checksums are enabled).
I only did standard SQL/utility commands to create, restore, set_search_path and analyze the 2 databases one after another without any error.
The first error that occurred was that the second alter database set search_path was executed without error, but had no effect!
Then afterwords other alter database set search_path commands gave the error of duplicate key.
The procedure is quite easy and straight forward: only create/restore/set_search_path/analyze 2 databases which have objects in other schemas as public.
The database size is about 1 GB in PG_DATA each.
If necessary, I can repeat the procedure on another machine, but please give me some time.
Thank you
Hans Buschmann