The reason is after an upgrade, there won't be any data in pg_subscription_rel, and only when you tried to refresh it is trying to sync again which leads to the "duplicate key value ..." problem you are seeing.
So, is pg_upgrade populating pg_subscription and not pg_subscription_rel ? It is doing 50% of his job ?
Don't you want to eventually upgrade the publisher node as well? You can refer to blog [1] for the detailed steps.
It is possible but I don´t think changing publisher will solve anything, will ?
Yes, the way you are doing I think it is bound to happen. There is some discussion about why this is happening in email [2]. AFAIK, it is not documented and if so, I think it will be a good idea to document
And my problem remains the same, how to solve it ? All records on pg_subscription_relare initialize with srsubstate null. How can I replay only updates since yesterday. This replication is a auditing database, so I cannot loose all things happened since that pg_upgrade. [1] points me how to upgrade but if I did the wrong way, how to solve that ?