The problem is that the passwords are saved the wrong way in Virtualmin/Webmin. As it seems this is handled in the file
I tried changing the old INSERT/UPDATE commands with the new one but it did not work.
I found a temporary solution and documented it here: https://www.virtualmin.com/node/64694
But the error is very annoying. Every user that we update destroys the database access to the database associated with this user. Please provide a hotfix asap.
Thank you! Marcus