Repmgr: an older version of the extension is installed but it's not true

I have a 3 nodes PostgreSQL cluster with PostgreSQL and repmgr.

Today I lost two nodes and I'm trying to re-clone it from the primary node.

If I try to clone it, repmgr complain that an older version of the extension is installed on the upstream node:

postgres@postgres3:~$ repmgr -h postgres2 -U repmgr -d repmgr -f /etc/repmgr.conf standby clone
NOTICE: destination directory "/var/lib/postgresql/12/main" provided
INFO: connecting to source node
DETAIL: connection string is: host=postgres2 user=repmgr dbname=repmgr
DETAIL: current installation size is 3484 MB
ERROR: an older version of the extension is installed on the upstream node
DETAIL: version 5.1 is installed but newer version 5.4 is available
HINT: upgrade "repmgr" on the source node first

But this seems not to be true, as the primary node is running the 5.4 version of the repmgr extension:

postgres=# select * from pg_available_extensions where name = 'repmgr';
  name  | default_version | installed_version |              comment
--------+-----------------+-------------------+------------------------------------
 repmgr | 5.4             | 5.4               | Replication manager for PostgreSQL
(1 row)

postgres=# ALTER EXTENSION repmgr UPDATE;
NOTICE:  version "5.4" of extension "repmgr" is already installed
ALTER EXTENSION

I tried to restart PostgreSQL on the primary node without solving the problem.

The error still happens and I really don't expect it to happen.

I also tried to execute the queries that repmgr executes to check the installed version, and I really don't see that the running version is different than the available one on postgres2 server:

postgres=# SELECT ae.name, e.extname,            ae.default_version,            (((FLOOR(ae.default_version::NUMERIC)::INT) * 10000) + (ae.default_version::NUMERIC - FLOOR(ae.default_version::NUMERIC)::INT) * 1000)::INT AS available,            ae.installed_version,            (((FLOOR(ae.installed_version::NUMERIC)::INT) * 10000) + (ae.installed_version::NUMERIC - FLOOR(ae.installed_version::NUMERIC)::INT) * 1000)::INT AS installed      FROM pg_catalog.pg_available_extensions ae LEFT JOIN pg_catalog.pg_extension e        ON e.extname=ae.name           WHERE ae.name='repmgr'
;
  name  | extname | default_version | available | installed_version | installed
--------+---------+-----------------+-----------+-------------------+-----------
 repmgr | repmgr  | 5.4             |     50400 | 5.4               |     50400
(1 row)

I've also tried to connect to specify the IP address on the -h parameter to be sure that it connects to the correct server but the problem is still there.

I'm really stucked on this problem and I have the cluster without two nodes.

Could you help me to understand where I'm wrong, please?

Thank you very much!

EnterpriseDB / repmgr

Repmgr: an older version of the extension is installed but it's not true #835