Thanks jtr.
No, I’m not using it, that I’m aware of. Not in the config.php file, not in the command launched.
I realised that I had a trailing slash in the datadirectory config as per [Solved] 12.0.2 to 12.0.3 Update Failes at "Create Backup"
I fixed it and now the log shows the correct path.
Copy is created, but it still get’s stuck there.