Postgres 9.6 to 12.7 pg_upgrade error - terminating connection due to administrator command

[Dhanush D <dhanushdk94@xxxxxxxxx>]

I am currently upgrading a Postgres cluster running on a Centos machine from version 9.6.22 to 12.7. Post the install of 12.7 binaries, I am running the pg_upgrade command:

/usr/pgsql-12/bin/pg_upgrade -b /usr/pgsql-9.6/bin/ -B /usr/pgsql-12/bin/ -d /<path>/9.6/data.old -D /<path>/12/data/ -j 12 -r -v -k

But, I am getting multiple errors during the "Restoring database schemas in the new cluster" step:

pg_restore: creating TABLE "schema1.table1"
pg_restore: creating TABLE "schema1.table2"
pg_restore: creating TABLE "schema1.table3"
pg_restore: while PROCESSING TOC:
pg_restore: from TOC entry 358; 1259 793395 TABLE table3 postgres
pg_restore: error: could not execute query: FATAL:  terminating connection due to administrator command
server closed the connection unexpectedly
    This probably means the server terminated abnormally
    before or while processing the request.
Command was:
-- For binary upgrade, must preserve pg_type oid
SELECT pg_catalog.binary_upgrade_set_next_pg_type_oid('793397'::pg_catalog.oid);


-- For binary upgrade, must preserve pg_type array oid
SELECT pg_catalog.binary_upgrade_set_next_array_pg_type_oid('793396'::pg_catalog.oid);


-- For binary upgrade, must preserve pg_class oids
SELECT pg_catalog.binary_upgrade_set_next_heap_pg_class_oid('793395'::pg_catalog.oid);

CREATE TABLE "schema1"."table3" (
    "date_key" integer NOT NULL,
    "col1" character varying(32),
    "col2" character varying(32),
    "col3" character varying(32) NOT NULL
);

-- For binary upgrade, set heap's relfrozenxid and relminmxid
UPDATE pg_catalog.pg_class
SET relfrozenxid = '1491955518', relminmxid = '1'
WHERE oid = '"schema1"."table3"'::pg_catalog.regclass;

Another log file:

pg_restore: creating TABLE "schema99.table1"
pg_restore: creating SEQUENCE "schema99.sequence1"
pg_restore: creating SEQUENCE OWNED BY "schema99.sequence1"
pg_restore: creating TABLE "schema99.table2"
pg_restore: creating SEQUENCE "schema99.sequence2"
pg_restore: creating SEQUENCE OWNED BY "schema99.sequence2"
pg_restore: creating SEQUENCE "schema99.sequence2"
pg_restore: while PROCESSING TOC:
pg_restore: from TOC entry 347; 1259 1949074 SEQUENCE sequence2 postgres
pg_restore: error: could not execute query: ERROR:  relation "sequence2" already exists
Command was:
-- For binary upgrade, must preserve pg_class oids
SELECT pg_catalog.binary_upgrade_set_next_heap_pg_class_oid('1949074'::pg_catalog.oid);


-- For binary upgrade, must preserve pg_type oid
SELECT pg_catalog.binary_upgrade_set_next_pg_type_oid('1949075'::pg_catalog.oid);

CREATE SEQUENCE "schema99"."sequence2"
    START WITH 1
    INCREMENT BY 1
    NO MINVALUE
    NO MAXVALUE
    CACHE 1;

Restore command from the logs:

"/usr/pgsql-12/bin/pg_restore" --host /var/lib/pgsql --port 50432 --username postgres --create --exit-on-error --verbose --dbname template1 "pg_upgrade_dump_16405.custom" >> "pg_upgrade_dump_16405.log" 2>&1

Similarly, at each run a different dump file fails (pg_upgrade_dump_16405.custom/pg_upgrade_dump_16404.custom). Has anyone faced similar issues during upgrade to Postgres 12.7?

There isn't much in the pg_upgrade_server.log file. It looks like the server starts and stops for the old and new data files. pg_upgrade_server.log file - textuploader.com/ta9o3 

Under /<path>/12/data/log. I see these lines:

```
LOG: background worker "logical replication launcher" (PID 35687) exited with exit code 1
LOG: shutting down
LOG: database system is shut down
LOG: database system was shut down at 2021-07-30 01:33:51 GMT
LOG: database system is ready to accept connections ERROR: relation "sequence2" already exists
```

I am getting an error even after only initDB and running upgrade. Any suggestions on what could be going wrong?

Thanks in advance!