Hello, I finally managed to solve this issue. It was due to the installed Ambari version not being available. repositories field of the repo_version table was empty for whatever reason. To solve this issue, I downloaded and edited Version Definition File from Hortonworks then I added a fake Ambari version using the + Register Version button / HDP-2.5 / Add Version ... / Upload Version Definition File. I updated other fields to match the initial installation. I then grabbed the repositories field from my custom Ambari version and updated the empty one with it. I restarted Ambari and voilà. The current version is now available and upgrade process does not hang anymore. I hope this might help. Kind regards.
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